My 2000 4Runner Ltd has developed a problem of stuttering/after firing. This only happens after engine is warmed up then shut off for 20-40min. This problem clears up after about 30sec-1min of feathering accelerator. If engine cools long enough, no problem on cold starts and engine will run for hours without incident. No CEL and mechanics have not be able to pull any codes. Have replaced plugs and wires with OEM and no change. Have cleaned MAF as well. Vehicle only has about 90,000 miles. Any comments are greatly appreciated...