Thanks in advance guys.
On the way home from a 6 hour trip through the mountains of PA I start to get sputtering and what appears to be misfires only under load. The truck is shaking and gasps and bounces when I accelerate. This continues to happen off and on for the duration of the trip. Not fun. The CEL flashed on and off once or twice, but never stayed on for more then 5 seconds. Next day I took it to my neighbors shop and he said the only code was P0300. I replaced the plugs and wires 2/3 years ago with OEM form the dealer. We pulled a plug and it looked fine. The MAF sensor had never been cleaned and was due, so we cleaned that. Ride home was fine, but the next day it started happening again. This time even at a standstill at idle the rpm's are bouncing +/- 200 and the truck is nearly bouncing. Took it back to him and there were no new codes. I am out of town on travel a lot lately and don't have the time/money to throw parts at it. I know that the common areas are vacuum, ignition, injector, fuel pressure, MAF, Engine coolant temp sensor etc. but not sure where to start. I just find it odd that no specific cylinders triggered a code. The problem is definitely intermittent as I drove it today with no issues. Any help is appreciated.

'98 3.4L 4Runner, 130k miles
original timing belt and water pump
newish (2-3 yrs) belts, plugs and wires

thanks

 

Check your ignition coils.