I am a decent mechanic but don't know everything so bare with me. I put on a short ram intake kit but the piping was 3" my stock maf housing was 2.5" so I taped it up to fit cuz I was broke. Ran perfectly fine for about 4 months. Finally got a new maf housing that's 3" and now it bogs down really hard in low rpms as if its getting flooded with fuel, but as soon as mivec is activated it runs perfectly fine. How do I fix this without a tune... Or do I absolutely need a tune?

 

The MAF sensor is VERY picky about the diameter of the piping where it is placed. The simplest way around this is to put the sensor in a factory sized piece of pipe at either the beginning or the end of the intake, and leave the rest of pipe whatever size you want.