i need help. here's my story. so i bought these used DC 4-2-1 headers online and was installing it last night. only to find out that the it doesn't bolt on to the cat! i got jipped! it was prolly for a b18 or delsol... anyways the main point was after i bolted the stock manifold back on i notice a loss in power in the lowend pf my power band. and also my engine check light came on. now, keep in mind that i also replaced the spark plugs. i switched to Bosch Platinum +4. im guessing its the manifold thats causing the problems. what does it sound like to you? is it the spark plugs? or the leaking manifold? does leaking manifold cause loss in power??
and if it is leaking, how do i check for it? initially i crawled under the car to listen to hissing sounds but there was none during idle.

 

MIL is probably on because you forgot to plug something back in (o2) Bosch +4s suck. I'd go back with NGKs. Honda puts them in there for a reason.

 

Why do Bosch Platinum +4's suck? After I got mine, they helped that annoying 4th gen Accord idle a little.

 

how you explain the loss in power? there is noticeable lag.

 

If the header isn't designed for your engine then the flow is "cut-off" and that decreases performance. Also, you might have not gapped those plugs, or maybe not tight enough.

 

what do you mean by "gaping" spark plug?

 

I agree, the +4's are garbage. Go back to NGK plugs.

If you have a leaking manifold, yes, you will loose HP and Torque. It will also kill your gas mileage too.

 

I think i didn't screw the spring loaded bolts all the way where the cat and collector connects. i'll fix it once i get my car from the shop.

im curious, why are bosch +4 crappy?