Yeah he's totaly right. I installed I,H,E on a 03 coupe,then a few weeks later installed a stage 2 stillen kit. The car only made 30whp over a Z with intake and exhaust. The stillen kit HATES breathing mods.

 

I dont plan on putting on headers or cats but just was interested in the Stillen TD. I have the stage 4 kit comming in next week and was just wondering if I should just put the stock muffler back on while im at it to see if it would make more power.