running too rich..

[Sleeper_DSM_817]

I have a question..can running too rich have an effect on gas mileage?

 

[timloomis]

yea,your putting gas in the cylinders that isnt getting burned and then get shot out the exhaust.

 

[blackGSX2g]

It most certainly does. Get a logger and see what your o2 sensor and fuel trims are doing. You also might want to do a boost leak test, as a leak in your intercooler piping would cause mess up your fuel trims.