Been a while since I've even posted on here but I've been busy with a few things. Actually been working on my buddy's 90 mustang gt on Friday/today. we installed some hooker longtube headers on car. Mostly stock when he bought it a few months ago, but after finishing up he has a big backfire on it. He didn't have a midpipe ready to go yet since he has one on the way. All he had was the headers running without a midpipe. We started the car outside the garage and don't know why it's backfiring like that. He didn't install the oxygen sensors since he didn't have the extensions. I'm thinking that's why it's backfiring, even without a midpipe. Am I wrong??