Sr20det redtop missing/backfire 4-5k

[rotation3x]

The car is a 90 240sx hatch with s13 sr20det. heres the problem....

If i start the car up completly cooled down and just get on it before its warmed up it runs fine lke it should.

after it warms up it starts missing/backfiring between 4-5k rpm... :/ kinda like detonation?

I checked for boost leaks all the way to my gauge. When it starts breaking up it dosn't drop boost at all.
I checked codes .... heres the thing, I had the issue before it gave a temp sensor and knock sensor code. I replaced the temp sensor and the problem went away for a month or so. This time I get no malfunction code.

engine free revs fine without missing/backfiring.

anyone have a problem like this?

I have had 3 different 240's with sr's and never had this problem unless it was a boost leak. I have checked and checked yet I feel its a stupid boost leak.

any suggestions??

[Driftbandit]

You should definitely check the wiring to the MAF, and the condition of the maf in general seeing how they're known to be sensitive. The wiring really needs to be done right on the MAF, as in not only are the wire colors matching, but is it also soldered properly and is the EMI shielding still around the MAF harness after extension. I've seen people strip the shielding while extending the wires. Not good. It's there for a reason. If it's dirty, or oxidized it'll throw the readings off and cause all sorts of problems. It's not uncommon to get a bad MAF with a swap or clip, especially if it has sat out in the elements. Try cleaning it with some canned MAF cleaner too.