I'm looking to buy the zzp header and downpipe. There combo is a 1.5in header with a 2.5in downpipe bolt in. The other was a 1 3/4in header with a 3in to a 2.5in exit bolt in for a little bit more. I'm curious to know if the larger header combo would show increased gains, maybe be a little louder, or actually take away from top end torque. What do you guys think?

 

Go with the 1.75" primaries.

/thread

 

^^^^

 

i believe 1.75" primaries are better for our supercharged cars, and i know mine's 1.75" and i don't have problems and i love it. Also, having a larger primary tube opening than the exhaust port is good to prevent backflow.

 

good stuff 1.75in it will be

 

with a 3in collector

 

1.5" and 2 1/2" downpipe is more intended for NA applications.