To tune or Not to tune?

[btwilson86]

I really don't, at low rpm and idle all the mods still don't really amount to anything more than stock, and its definitely within the capabilities of the stock fuel system. Until you build boost, you're still under vacuum, meaning there is no additional air being forced into the engine. After I did all my mods, I was at -16inHg at warm idle. After trying like hell to fix a misfire at idle, I eventually found vacuum leaks I could not detect (mostly in intercooler couplers, one big one was a split in my accordion hose where it slips over the turbo), and my warm idle vacuum is now at -20inHg. So I have more vacuum now then I did with my old setup, which means the engine is drawing in more metered air then before. I eventually found out that the random misfire I had at idle was actually a bad AFM. It turns out when the compressor wheel on my old turbo grenaded, a large chunk of it hit the stalk inside the AFM and must have done just enough damage for it to occasionally get poor readings and screw up my air/fuel mix.

I assume that since you're adding power mods, your car was running in great shape before this, correct? Also, have you checked for engine codes since the rough idle started?