Bill is right on the money with his explanation.
That was the key to my Bonne being the quickest last year even when running against similarly modded cars using slicks. Richen up the mixture with the adjustable fuel pressure regulator. I have been running the stock 36 lb injectors at 6 psi higher than stock to equivalate to 43 lb units.
The Snow kit for 96+ GM will work for any OBD2 GM car. It gets its voltage signal by connecting one wire directly to the MAF sensor output. It then regulates off the frequency of the MAF by converting to a voltage. There are 4 different ramp rates you can choose from using dip switches based on the specific MAF sensor voltage. There are two dials that control start and max voltage to control the range.
It is expensive and it doesn't take long to use up half a gallon.
Maybe if I had to do it again, I would install an intercooler.......but this is fun for now.
Oh, I almost forget another cool side benefit. After letting off the gas pedal when using the injection and then gearing down so the engine is under compression braking....the extra rich fuel mixtures blows flames out the tail pipes.