Scraping noise...

ok i need help because at this point i have no idea what it could be, whenever i have more than 2 ppl in the car with me and i have the windows down i can hear a scraping sound, and ive changed the shocks and the struts in the rear but i still have no idea what it could be, so yea when i go its just scraping, and when i slow down it stops untill i go again, and lets say im bymyself or something just driving around, if i like hit like a little dip on the road, when the cars weight transfers back down u hear an initial scrape. but yea any help would b appreciated cuz i would really like to know what the noise is. and btw its a 1994 V6 5-speed Mustang

ok well i know its not the exhaust, and the ppl arent fat, lol it never did this b4, so i dont understand... also i notice that when i have the ppl in the car or it seems that the right rear is lower than any other side of the car if that helps. i would really like to get this problem fixed and i dont want to take it to a mechanic cuz ive taken it twice for this and they replaced the struts and the shocks and it still does this crap *Sigh* anyway anyone else have some input? or having the similar problem, cuz normally it didnt bother me till just recently cuz i go out alot with my g/f and we usually go with other ppl so ill take 2 more ppl with us which is just 4 ppl so i dont see how that would b too many ppl and these are all skinny ppl, the stupid stick on the inside of the door thing says max. capacity 4 ppl then why wont 4 ppl fir withought that damn noise, lol anyways any help is appreciated once again. plz...