I dont know how the slp would sound on the GTP but I have slp loudmouth catback on my 02 mustang GT and it sounds incredible. 1 year now and a new england winter covered in snow and salt and not a spot of rust. Try looking on youtube for exhaust clips and see what sound you like best, then ask the poster about the quality issues like fitment and corrosion. It might be a lil footwork but it beats spending your hard earned money on something you aren't completly happy with. I personaly hate buying things twice.
