When I had an 3.8 firebird I have put an aftermarket exhaust system, huge muffler & then my 3.4 camaro.. When I turn my firebird on cold days like this, its dual exhaust on it was equal & my 3.4 it favor the left side more then right.. Can anyone explain this ??? Please

 

I have Magnaflow on my 3.8 and at first its the same, then about after 2 minutes it favors the right, till about half temp 160 or so then evens out to favor both.