I was runnin stock hearders n stock h pipes on my 90 5.0 stang. I took it to my general mechanic to swap on som bbk shorty headers with x pipes no cats.when I picked it up n drove it back home I notice it was a lil bit quieter but that wasn’t my concern my concern was this noise it was makin as soon I give it som gas the more i floored it the louder it sounded like if I was drivin a gotdam DIESEL when it juz idlin it doesn’t make that noise like I said only when I give it som gas...so what can it be? my mechanic did a half ass job or what? But I hav notice when swapin headers som get that noise on any car n I also got a truck n I also swap the headers n SAME