okay i bought my car from a guy it had gm stage 2 and a knn cai when i got it it said running rich an supercharger bypass valve. i lube the by pass valve that code went away soo the running rich was still there i changed the 02 sensor and cleaned the maff in the intake tube. i took it to the dealership they could not figure why it was running rich as well as two other shops. i finally went and got it tunned with hp tunners the tunner said it was takin 20% fuel at idle he fixed it and all that after he tunned he drove it and said it was way slow compared to the other ones he has tunned with the same exact setup. it does not have near the power it should i also noticed its kinda stuggles to go pass 120 i do not know where to go at this point any help woud be great accelertaion seems sluggish oh and another thing alot of black smoke comming out of exuast when i rev it up please help!!!

 

black smoke is because of it being rich

you need to get a wideband and see what your AFR is

 

Get a custom tune, it will solve your problem and give you extra power.

 

whats a good wide band?

 

Either aem uego or if you have money, buy an interceptor gauge with wideband

 

So you had a tuner tune you without a wideband

 

Or tuner had a remote wideband that goes into the muffler at the tip

 

True

 

i use the AEM