Thread: wondering idle and dies out?

Did a JDM DE swap in my NX and since then it's had some problems similar to a vaccuum leak. No matter the temp the idle wonders from 1k-2k most of the time and the rest of the time it sits at 900. It also dies out when i let off the throttle most of the time. I tried unplugging the IACV while idling and it died out. Now there is no CEL also. I checked under the IM for vac leaks already. There's 3 vac nipples on the JDM IM that i saw-one for the FPR, and the other two are plugged and they're all by the TB-one small one like the FPR, and a slightly larger one. I also took the rail off and put new orings in the IM. The intake hose vac nipple is plugged also. Is there any i missed? It also seems to run a little rich. It pops and backfired when i let off the throttle. This tells me it could be a vac leak i just have to find it right?
Any help appreciated

Timing
MAF voltage
lambda
AAC
opening of the temp valve(s) (sorry, lack the proper English here)

Maybe this isn't helpful at all but I'm trying to help.

probably your timing is set too late, causes excess fuel to build up in the exhaust which POPS or as you call it backfires when oxygen reaches it from the exhaust end tip.
also your spark plugs could be smudgy because of misfiring, did you replace them?
if it misfires youll lose performance because the engine needs to work harder to turn the crankshaft because of the "dead" cillinder. als your injectors could be clogged, did you run out of gas once? could be that the mess in the bottom of your fueltank has been sucked up by the fuelpump and entered through your injectors causing blockages, causing misfires.