I have a '98 6.5 that I'm having an issue with. I'll try to explain it the best I can, ask me questions if you need more info. After my truck gets warmed up (traveling more than 20 mi), it wants to surge and accelerate like you wouldn't believe. When I say accelerate, I mean, I couldn't make it go this fast if I went WOT. Boost gauge increases and flutters. Exhaust temps go up by 200 to 300 degrees. It only does this for maybe 3-5 seconds then it falls on its face. Has no power and acts like it has no fuel for a couple seconds. It feels like I'm riding a buckin' bronco. Back and forth, back and forth. After acting up for a few miles, it will run correctly for a few and then start acting up again. It does all this on cruise or holding the foot feet steady. It has also died at idle a few times. It will always start right back up.

After researching this site I have done the LP test (checks out ok) and replaced fuel cap (was hearing some vaccuum when I'd take it off). I'm leaning towards trying a new PMD. From what I've read a pmd will act up in various ways. And since it only does it when warm also points to heat buildup in the pmd? Only other recent mods have been a 4"exhaust and new injectors (107,000 miles, figured it was time) Any tips would be appreciated.

Try a PMD, if that fixes it make sure to relocate it away from the engine heat , if you haven't already done that. Wierd surging can be a common sign of PMD failure.

Remove the Toyota floor mats. LOL. Seriously get that fixed. I would hate to see anything come bad out of something like this. Something like this happens to my wife while driving, she would sell the thing right there.

sounds like the same thing mine did except it would just keep going, i changed to my spare pmd and it stopped