[skipster04]

the backfire would be from being a bit on the rich side and that could also explain the power issues. If you had a plugged cat when you first tuned and you've since had that fixed that would change everything compleatly especially if you used the wideband that goes in the exhaust that dyno's usially have. also do you have a wideband o2 sensor in your exhaust before your cat? the fuel map is what is going to change your a/f. do they require emissions testing where your at because if not, take that thing out, it will make your turbo spool much faster without the back pressure it creates. also $700 for a tune?! wow you need to find a differnt shop.