well um I was bored so I got myself a header for my 7th gen civic ex... didn't expect any performance gains but like i said, just for fun.

anyhow, after the installation, I'm having some problems.

I think I have a leak somewhere... since I can smell the exhaust fumes easily when I open up my hood.... I feel like fainting right now in fact, smelled it more than necessary today. the car also makes a rattling noise... you know those noise a car with a broken exhaust system makes? yuck.

I didn't replace the stock gasket yet... only had the car for 15,600 miles, should I replace the stock gasket?

I overtighten one of the bolt that connects the header to the heaer, and now its sorta loose. you know how you can turn it and it gets tight and tighter and then suddenly it becomes loose? and the cycle repeats as you keep on turning the bolt? is that because the bolt is stripped?

and finally, there's an opening for a o2 sensor, and I plugged that up with a 3/8" bolt... I couldn't super tighten it because my socket wrench set is metric (mm) and I didn't have any that would fit the 3/8 easily... so I just used a monkey wrench that has little or no torque.

anyhow. anyone got some ideas whats wrong? I think the leaks could be any of the ones listed above, but I really can't figure out the rattling.