Help a newb figure out what mods are on 91gt

take some pictures of the engine and post em up!!!!!!!!!!!
c5's arent really that great by the way. it's not too out of place for a worked 5.0 to hang or beat one. the zo6 on the other hand is a monster........
without pics to go by, it's really hard to guess.
the biggest things you need to look at in the engine are the heads, and the intake manifold. any part numbers? brand names etc.... those are the main visible parts to guess at what you're running, without taking things apart...
or take it to a dyno, and see the #'s.... not precise, but it'll give you a better idea of what you might have.....

Post up a couple pictures of the engine bay

What color are the fuel injectors?

Open up the oil filler tube and see if you can see roller rockers...

If aftermarket, many will trim or remove the oil baffle.

Congrats on the car

If you're hanging with a healthy C5 then someone has done something. They are mid 13 cars.

Pinging usually indicates a lot of timing. You may want to check and see if the spout is installed. Look at the cable coming from the dizzy. There should be a short connector coming off of it with a grey plug stuck in it. That's the spout. When it's removed the timing is locked. That would explain the lack of advance when you rev the engine.

With traction it will run 13.7s as is.

The code 22 can have a significant impact on performance.

Code 22 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture by sensing changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it. There is no way you can use a common cheap voltmeter or DVM to accurately measure the output signal.

The MAP/BARO sensor is mounted on the firewall behind the upper manifold.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.

Tremec transmissions:


Tremec 3550/TKO



Tremec T5

See http://www.ttcautomotive.com/ for a full listing ot the TKO variants

the loud, whiny pump might be a bigger fuel pump. does it have the factory mass air meter? measure the inside diameter of the throttle body. for the rest, you're probably going to have to start taking things apart.