I had a prochamber, loved it. Youll keep more bottom end with the Prochamber, but it wont be as loud as just a plain H pipe. Still loved the sound and power it gave me though.
BBK's are great quality, Macs seem to have some issue with the 4V cars, but perhaps they were fixed, but Id still be wary. SLPs are expensive but great quality. If I were putting them on, Id get BBKs and change the clutch when I did the L/ts.
Forego everything else and get 3.73s and a Mongoose Supercharger kit. Nothing will give you bang for the buck performance on these cars like gears and some sort of forced induction, be it a blower or nitrous. I noticed NO gain from my 50 dollar K&N air filter, and will not buy another one for...
If you feel the clutch is slipping, then Id change it, otherwise, ride on that one for a while til it does die. Also, get the codes read on the CEL and see what it is. Make sure he hooked the mils up.