I have a DC 4-1, AEM CAI and an Apex n1 on my 01 R. Ever since installed, I loss .2 in the 1/4 and running rich. The dealer claims it is the header because not enough back pressure. How is this possible if the JDM has a 4-1 and no problems?????

 

What DC?

 

It's the USDM DC 4-1 I think. He is still using the stock cat. Does the car FEEL slower? Did you reset your ECU? There are many factors that could cause your 1/4 mile time loss. Don't expect too much from the DC 4-1 with stock cat.

 

It is the USDM 4-1. If it is the stock cat causing the problem, what should I get to correct this? Will I have a problem with emissions if I change the stock cat??

 

The cat is just limiting your exhaust gas flow in such a way the you don't gain much from your DC header. You can get a High-flow cat or test pipe. You won't pass emission test with a test pipe. But how did the car FEEL after the mods? Stronger? No difference?

 

The car felt like it hit v-tech harder but it lost .2 in the 1/4.