84stang.

the misfire i cant really tell if its at idle and high rpm ... but i know its at idle for a fact... now im running shorty headers into an x pipe then straight pipes.... someone told me this sound could be a cause of little back pressure..... Is that possible.... Will mufflers fix this problem and give me more hp? Might be a stupid question.... But..... And also.... My header bolts keep vibrating lose i did not want to put threadlocker on them cause i thought it would bake and if i tried to losen the bolt it would break off in the head. Header locking bolts?