hawksftball2007

OK so the other day i swapped out my exhaust on my 98 civic lx; header to muffler with a y8 setup. i had the y7 with cracked header so swapped it over and extended the o2 sensor. no check engine light etc. but it seems like when i am accelerating i hear a sucking noise from under car, you really hear it when under bridge or going by guard rails.Idk if its just because the less restrictive header or catalytic converter since its more straight thru on the EX exhaust. I looked and exhaust is not leaking at all i have not checked the 2nd o2 sensor for tightness but i figured if no light then it must be working. Car is completely stock besides lowered. any ideas of what it could be, exhaust or something else? Thanks

btw i put car on jack stands and accelerated and couldnt hear anything, but only happens when pressing on gas, once let off it stops

ehrkeith

Intake sucking in air? I only hear that sound under load like you are describing

bluedragon

Easy way to see if its leaking use some sea foam or some care cleaner make it car smoke that's how i found i needed a new gasket fourth header