I read your post l would remove throttle body turn on side that opposite of throttle moter spray carb cleaner and clean butterfly plate in side it gums up and causes surging or hunting do not let spray get near moter housing hope this helps

I have a similar issue in a 8 series.
If you death head it or lock the wheel the truck surges at times and will stall randomly.
We have replaced the vacuum chamber at the vaporizer and some one installed a new vaporizer also. We have tried the adjust the mix and it's at 2.5 and the 02 cycles normally.
We went as far to Install a new distributor and still doing the same thing. Other then a ecm not sure what else controls the compensates load.
Thank you.

When reading this is at first sounded like the pre LPG FLT that Toyota is using it's a 3 micron flt and clogs a lot faster an the old 10 micron flt the new flt it located to the right hand side over head guard it round and has 4 10mm bolts those have been clogging a lot on me casueing this symotom

Glad to hear you got it fixed. Sometimes the little things cause the biggest problems. It also pays to keep looking as you did for the root to the problem.
We have several of the 7 series but I haven't had that problem yet but it will be something to watch for.

Well we seemed to have found the problem. Someone had tightened the idle mixture screw on the propane converter to tight and damaged the needle. We cleaned up the needle and everything was great. Thanks for your help.

THanks for the reply. There aren't any codes on the lcd display. We are sort of heading towards the TPS as well but just looking for support in our decision. We called Toyota and they want about $300 for the TPS. Iguess we'll keep digging to make sure. Thanks again.

Hi Wil, Is there any other lights on the dash on? Look at your hr/combination meter and see if any error codes are set. If I am not mistaken you can just turn the key on to see codes in hr meter.
Just a guess but it sounds like throttle position sensor but with out scanning hard to say.