They fit well. 1994 k2500 350tbi. I was able to bring both up. They sound good and performance has improved. I don't know fuel consumption yet. Now for the bad. When you put it on, make sure that the truck is running for a long time so that the paint burns off completely. smoke something nasty I thought I had a fire under the hood. Second, the bolts they use to mount the exhaust pipe are crap. I installed them and after half a day the bolts came loose and I lost my left exhaust pipe. After examining it, I found that the other side had almost fallen off as well. I used a torque gun on the bolts and they still came loose. I don't know how many people have had this problem, but if you buy them, check their screws a few times after installation. And that after several trips. I will buy screws a little longer and swap out the ones that come with them and drill holes in the screws. Just go where the nuts would sit and insert pins to hold them in place.