Guys, i got a question and i might be a stupid person but hear me out...
I got some megan Jspec racing headers 4-1..great style of headers i love it and i noticed a improvement, my exhust now has those headers, a 2.5 test pipe, and a 2.5 piping setup from the cat back, to my apexi n1 muffler..
Problem.. i haven't really raced anyone fast lately until last night, i raced a fully built gsr hatch .. and it spanked me..hard.. like 3-4 car lengths and i really dont care that i lost, its the fact that i've raced a car simliar to thise with my stock exhust and whipped his ***, my problem i think is because the collector on the header is 2.25?? and the inlet on the test pipe is 2.25? and the out let is 2.5..is this bad?? i mean is this something i should consider wounding out to 2.5? or what.. i think these headers helped, possible i need to bring my car back on my labtop and retune it, i mean i'm running alittle lean, was running 12.9 now at around 13.2 and 13.3.. i mean i dunno any info this motor is spinning up to 9300 its flowing enough air out of it to use this big of piping but wtf is going on??

 

the collector/test pipe inlet is bottlenecking your exhaust..but even w/ stock motors ppl see gains from a 2.5" header...

but street racing is not indicator of how fast your car is..just cuz you beat one car one time, and lost to another that is similiar, you cant say your car lost power..
too many variables on the street to tell what happened...