Adjustable fuel pressure regulators are high 'bang for the buck' upgrades. They allow you to additionally tune your fuel system by precisely adjusting for optimal pressure. Cutting back on fuel pressure will decrease fuel to the injectors. On stock Probes, decreasing fuel pressure and leaning out the air/fuel mixture will add a considerable amount of power. If performed correctly by a knowledgeable mechanic with an air/fuel ratio meter, the fuel can be leaned out to provide as much as 5 to 10 horsepower. The downside is, improper adjustment can easily destroy an engine. Even minor adjustments can yield a respectable 2-3 horsepower.

Adjustable fuel pressure regulators can also be used to increase fuel pressure and allow the injectors to flow more fuel. This can allow you to increase turbo boost or nitrous oxide using stock injectors.

Venom Performance offers a set of injectors for Probes that are considered OEM replacements, but are designed for improved performance at equal flow rate. For an additional fee, Venom offers an upgrade for these injectors that improve flow by 8%, which would be good for engines that have modest performance improvements. For high performance needs, Venom can custom make injectors up to 1400cc.

It's very important to consider your goals when purchasing larger injectors. Although all injectors can be adjusted through fuel pressure, the pressure and flow rates that they are designed for will produce the best spray pattern. Installing injectors that are too small and increasing fuel pressure to compensate will not offer optimal injector performance. Installing injectors that are too big and decreasing fuel pressure to compensate will cause idling problems.

This upgrade is most effective when paired with a high flow fuel pump. Installing injectors that are too big can ruin fuel economy and cause an overly rich fuel/air ratio.

Personal Experience: A purchased an A'pexi Super AFC for my '91 GT. It wasn't meant to be used on a Probe, but after hearing that a fellow Probe owner managed to get it to work on a second gen, I figured I'd give it a try. Unfortunately, it turned out that this unit cannot work with the first generation Probe's air flow sensor. This was a BIG disappointment to me.

I'm currectly seeking other fuel management systems for my '92 GT.

Performance and race engines with upgraded fuel systems will benefit from performance fuel filters, since they allow drastically increased fuel flow and minimal effects on fuel pressure. Most are lifetime filters that you can either clean, or get inexpensive element replacements. Effects will be extremely minimal on stock systems.

As performance modifications are added to a car, a higher flowing fuel pump becomes more necessary. Increasing boost pressure, adding a turbo, or injecting nitrous oxide into the engine are instances where a high-flow pump is highly recommended.

High octane racing fuels, such as Cam-2 and Cam-4 will improve power throughout the rpm range. Cam-2 and Cam-4 are 102-octane and 104-octane fuels that burn with a slightly purple-tinted exhaust gas and a sweet smell. When the engine is tuned correctly, they'll provide better gas mileage, overall cleaner running, and of course, more horsepower. Higher octane fuels ranging from 110 through 118 would definitely be for track use only, since they are designed for high compression engines. Unfortunately, the downsides of these fuels are numerous.

First, unless your engine is tuned specifically for higher octane fuel, you won't get any power improvements. Using higher octane fuels on engines that aren't designed to run on them will basically be the same as running lower octane fuels. So unlike what most people think, using 91 octane fuel in a stock 2.0L engine will not improve its power, since it's designed to run on 87 octane fuel. To use a higher octane fuel, you'll need to have a computer chip upgrade, such as a SuperChip, but having your engine programmed to run on 106 octane fuel will get extremely expensive.

A big factor of buying high octane fuels is their cost, which in my area, run about $4 to $4.50 for Cam-2 and $5-$6 for Cam-4. That could be $60 to $90 for a single tank of gas.

Higher octane fuels provide more power by burning slower and hotter. This will cause a considerable jump in engine temperature, especially when running 106 octane or higher. These higher temperatures can be damaging to an engine.

Then there's the legality part of it. I'm not sure what laws are out there on this, but I know that in New York, it's illegal to run it in a street driven car. Gas stations around here can sell it, but you have to fill a gas can with it and fill your tank yourself at home.

Lastly, although I'm not sure how many people will be willing to spend $15+ per gallon on 110 octane fuels, but people who do need to remember that fuels with octane ratings that high are usually leaded fuels. Leaded fuels can harm exhaust parts, such as oxygen sensors and catalytic converters. 

The Venom 400 Performance Module is an add-on control module that adjusts the signals to the ECU to alter your vehicle's performance. Although Venom suggests performance is improved by altering the system's fuel curve, its main feature is to alter the transaxle's shift points based on throttle. Normally, under normal load, the automatic transaxle will drop a down gear when the throttle reaches about 60-75%, and if there's room in the rpm range, it'll drop an additional gear between 75-100% throttle. With the Venom 400, the transaxle will shift to the lowest gear possible at only 25% throttle. This will make the transaxle considerably more aggressive then stock. Fuel economy will take a considerable dip, due to increased engine speed.

Since the unit is geared toward automatic transaxles, the unit will most likely offer little, if any, improvement with manual transaxle controlled vehicles.