I just bought a 91 Gmc 2500 4x4 and it seems a bit slugish. A couple of my more mechanically inclined frieds felt that i had a major restriction in the exhust so I just put dual exuast from headers back with with 2 flow masters on her and still seems to be the same.(needed to be anyways way to quiet) So now I am thinking of getting the thermo hypertech chip. Need some opinions from people who have done this and if this is a worhty mod or not. I do use this for my landscape business and am pulling a trailer alot!!! Also how did your gas milage change with this chip....better or worse. Thanks all in advance!!!!