I recently bought a evo two weeks ago and im trying to figure out why im having idle issues and poor performance. im getting the p0171 code that says system too lean. the car is my winter project so she wont see any street duty until these issues are fixed.

 

you can email me the rom @ tuning@vr-speed.com and i can give you my opinion on it. is it a stock evo? is this your first turbo car?

 

It might be caused by a problem with the MAF (might be dirty or broken) or the injectors (damaged and or dirty) .... also there could be a vac leak somewhere (but in my opinion thats a symptom of everything but never the actual cause haha)

You can upload your ROM to a file hosting site and provide the link

 

here is the rom. car has a boost controller,injen uicp/intake and a catback. not sure if it has cams or a walbro. compression is 170 all the way accross
http://www.mediafire.com/file/wu2f8sr1yers741/jeff.hex

 

The ROM looks alright, the only thing i noticed is that at 2 bytes at address 0x003FFCE and 0x003FFCF are different; but I don't know what that data refers to. (probably nothing to be worried about)

You mentioned that you have an intake along with an uicp; on some occasions this can skew MAF readings and might call for a rescalling of the MAF (but personally I've never encountered such a problem.)

Can you provide some logs which include MAF readouts along with Fuel Trims, etc.