I am about to order the zzp header and d/p combo should i get the 1.5 in or the 1 and 3/4 also i have a megan exhaust i wanted to get a 3'' d/p or should i just stick with the 2.5''

 

1 and 3/4" primaries unless you're pushing under 180 hp or so. A 3" downpipe might help out better than a 2.5", but i'm not sure.

 

1 3/4 primaries with 3" collector to a 3" dp with 2.5 exit. you can always go 3" exhaust in the future that way

 

If your not getting above 300whp you dont really need the 3 inch downpipe cause you are going to lose so bottom end torque with the 3inch

 

What he said. I have the 1 3/4 primaries with a full 3" exhaust (cat-less DP) on a 2.8 pulley. Lost a noticable amount of power in the low end. The car is still quick but it doesn't come alive untill about the last 2k RPM. I have more mods in store for my car so I figured I would deal with the loss of low-end for now and not have to re-vamp the exhaust later when I'm pushing more power.