Has anyone installed one on your '99, 5.7 Vortec engine? What gains if any did you experience? Right now on my wife's Sub, I put in a K&N air filter and had a Magnaflow muffler with dual exit tailpipes installed behind the rear wheels. Sounds really SWEET. Just looking to increase the gas mileage a little.

I recommend the airaid poweraid TBS. I never dynoed it, but im guessing it picked up 5-7hp and has increased hwy mpg by 1-2 on our fleet trucks

I just purchased one from TNT Peformance out of NY. Will let you know what kinds of performnace gains we get. :smokin:

I have the poweraid also. Seems to work OK. In my opinion, the two best power/MPG increases were the headers and a MSD 6A ignition with coil. I have tried many other things including an underive pulley set. Most were not very effective for the money and effort spent.

I also bought one from TNT last year after I bought my suburban and wanted to improve mileage. I think it improved city mileage by about 1 m.p.g. haven't really checked it highway since but I would assume that if it increased city mileage 1 it should increase highway 2-3 m.p.g.