ok o got a stock evo 9 mr with 14 g miles on it and i put a HKS ti carbon muffler 3in all the way cat and res. deleted and just installed a megan racing o2 houseing and it used to spike at like 1.7 bars and than going down to 1.4 bars it starts at 1 bar than goes up to like 1.4 is there something wrong or is this how it is soppsed to be????????? please help cuz i am gettin a tune this weekend form mellon tuneing please help!!!!!!!!!!!!!!

 

mellon will answer all ur questions and ur post is kinda vague. basicly the exhaust and o2 housing will really open up the exhaust causing u to boost more. when i did my full exhaust and o2 housing without touching n e thing else i gained around 3-4psi of peak boost