'97 Ranger dies/hesitates at idle

Asking this for a co-worker. He's been looking at a '97 ranger with the 2.3L engine A/T RWD. It starts fine and runs fine. After revving it up to 3k RPM or so and quickly releasing the throttle, it idles rough and low, and will occasionally die. Spark plugs/wires are good (both sides), it has good fuel pressure, injector pulse width, good even compression, timing is good. He has checked every single sensor, and unplugged them one at a time to see if it made any difference. He even disconnected the P/S pressure switch. The timing belt was cracked pretty bad and a little loose, and was replaced. We checked the IAC motor, and even tested with a new one. Made no difference. Ignition scope looks good. It has a p0300 which sets when it almost dies. We checked all TSBs and none fit. He did an induction flush which didn't help at all. We tried turning up the idle speed a bit to see if that would make a difference, and it doesn't.

There's a good chance he did something I didn't list, I've been over there looking at it between my cars and at the end of the day, but that's the stuff I've been there for and/or asked if he did.

Thanks for any help
Jason

I have a similar porblem with my 01 2.5 M/T. Sometimes if a rev it hi and then realese the throtle it will idle low but i dont let it die. I gues is just something that rangers do.