My stang is in need of a tune which I get for 75$... But its been having problems with the a/f ratios and its been running lean and back firing on idle and rev ups.. now my question to you do I need to replace the 02 sensors and it will take care of the lean, backfire, hesitation? Or do I get the tune? See the thing is money is tight and can't get both at the same time.. what would u do first?

 

whats modded on the car?

 

Of course the one post yall need to know my mods my Sig doesn't show up haha. 03 PI Engine Swap, True Duals, BBK LT Headers, Off Road H-Pipe, Throttle Body, C&L CAI, 93 Octane Tune, Catless, Under Drive

Pullies, Bullit Rims, Grabber Blue & Nitto Drags

 

id try the tune first, that pi swap will raise compression and flow better.

 

School boy - If im not mistaken the OP swapped a complete 03 motor in so therefore there wont be a raise in CR. There would only be a bump in CR if he just did a pi swap

 

correct

 

yea, i see that now. thanks for the catch. but even with the pi engine swaped in, stock to stock, the pi will be about 20-30 ponies more than a npi. plus the full exhaust adding to it. if that 93 tune is for a npi engine, i could see it running a little lean. but then again, ive seen mark viii swaps use the factory 2v tune and not have any issues but i dont think the air/fuel ratio was every checked.
how long was the pi engine in the car before the issues took place?

 

Bout a year

 

O2's first, then the tune. Had a full bolt on PI swap 98GT with a stock tune and it was fine.

 

Or a simple vacuum leak...