x-posted from the 4th gen forum for more visibility...
Little background on the car: 103k miles, turbo, shortblock and head internals replaced at 60k, zero oil consumption. currently have catted DP and exhaust, turbo inlet, AP OTS stg 2 tune (91 octane, fill with 92) and homebrew AOS. My idle is lumpy and i get an occasional plop plop noise at idle along with a little stumble that you can feel. doesn't really affect the RPMs, on my AP sometimes i get roughness in cyl 3 that matches the stumble it has been as high as 12 but is usually around 2-5 sometimes it doesn't pick it up at all. The surging usually comes between 2k and 3k and steady light throttle. under moderate to WOT acceleration it is smooth except for the normal hiccup or shudder in that rpm range. i get no roughness readings anywhere but idle. vacuum seems to be good at ~20mmhg at idle and it hits peak boost fine so i don't think i have any leaks.
I have cleaned the MAF and reset the ECU to no effect. Where should i start looking before i go buying new cam sensors, PCV, OCVs, spark plugs, injectors in an effort to try and hunt this shit down? other than this crap it runs strong.