1997 f350 just bought getting 10-12 mpg

[Red0525]

I just bought a 1997 with 7.3 in it cold air intake 4" exaust. It was pushing 20 boost when I bought it I noticed couple days later it wouldn't go higher then 10 anymore so I had a Freind hook his tuner up to it on stage 1 that brought it back upto 20 boost but I was only getting 10 mpg. We disconnected the tuner toook the PCM out it had a bit of water damage so we cleaned it up put it back in serviced the truck including fuel filter afterwords I was pushing 20 boost again without tuner but now I'm only getting 12 mpg. Truck has a 6" lift with 35" tires. I have three freinds have the same combination as me except one has a turbo going out and there all getting around 17-19 mpg. Any ideas on why I'm getting horrible fuel millage?

[jdman49]

sounds like an injector or idm issue. does it smoke at all?

[Red0525]

It smokes a bit when I start it cold but it's a light blue color smoke.