[saj]

I NEED TO MAKE A POWERFLOW SYSTEM FOR ME CAV MK2 SO IT MATES UP WITH THE GSI DOWN PIPE WHAT IS THE BEST BORE SIZE SO I DONT LOSE POWER.

 

[Dave Dixon]

Just take it to your local Powerflow dealer, and they'll make one for you!

 

[Nickrp1210]

i use a 2.5" system from manifold back it seems ample i have heard of 3" systems but i have also heard of them losing power lower in the rev range because of lack of back pressure so i guess it all depends on how you want your car to behave. sbd recommended me the 2.5" any more and the power output would be too steep for day to day driving

 

[LEE69]

2" is standard.