Good News first: Over the last week, I installed my fenton headers along with a new water pump (old one crapped out) and drove the car (open headers) about two miles down to the exhaust shop to get my smithys put on and all the piping done. Bad news: When I went to picked it up on Friday it was running like crap in the shop. the engine seemed to idle rough and there a bad intermittent creaking sound coming from the car that sounded to be rpm related. (meaning when I gave it throttle I didn't hear it until it started to idle again.) Nothing looked like it was banging from the exhaust work, it wasn't that type of sound. The shop said they weren't sure where the sound came from. I drove the car down the block to the gas station and it performed well, wasn't sluggish at all. However when I came to the gas station to slow down it seemed to idle rough and I heard that sound again under the hood. So I check the oil and put some gas in. Oil was low about a quart so I put some in and fill up the gas. got home just fine and I pulled the plugs. Every single plug was BLACK with carbon build up. So I replaced the plugs with new one and fired it up, it idled a little better but still heard the same creaking sound and noticed a cloud of exhaust smoke and smell. I shut off the car and check my #1 plug it was starting to look black again. Oil dip stick is fine. I reset my carb mixture screw back to 2 1/2 turns out per manual and adjusted my idle screw, the car still had the same issues. Anyone had similar issues after putting headers on? Any potential fixes? Is it an exhaust leak?