Bad accelerator pump on EFI 5.8 (Ping Jim Warman)

Any codes?

I'd suspect TPS... PCM looks at TPS - if it can see it moving "open" rapidly, it can respond faster than watching for a change in MAF... without this "warning", the motor can stumble... Easiest way to test is with a HIGH IMPEDANCE analog voltmeter - back probe the grey/white wire and, with the key in run, sweep the throttle looking for smooth voltage change with no dropouts. DMM will work but, if the tool scans too slow, any faults can get lost between scans...

Possibly ignition problem? The increased cylinder pressures will cause a rise in required voltage at the plugs.... suspect weak coil or a secondary ignition leak.

Possibly fuel pressure but I would expect this to cause other concerns as well....

HTH

Oh yeah, the TPS sounds most logical especially since it's intermittent. They are inexpensive so I must just go on and change it. If that doesn't stop it then start looking at the ignition. It has just shy of 100K very hard miles as a company truck.

Let us know what you find....