Kreeess

hey guys, been noticing smell of fumes inside the car when front defroster is on, I am currently running LT headers with no cats, I understand catless it will have some smell but I dont think its supposed to be entering the cabin is it?
what should I do?
Do you guys know or recommend shops that can maybe do a smoke test or figure out my issue? I've tried few local muffler shops and they dont wanna take my car in since its "too low"

thanks in advance