That is what l was talking about what is wrong is inside the injector holder there is two pipette valves they are stuck cause for the propane to blow to air cleaner

Thanks for the advice. The cleaning of the main injector did not improve the symptoms. We ended up replacing the assy that contains all 3 components at the carb area. It solved the issue. Sad thing is, we don't know which component was the culprit. Thanks for the help.
Erich

To tell for sure if it's running lean you would have to have access to scanner and look at short term fuel trim to see if computer is trying to riching mixture l have seen the injector holder relief plugs clog up you could try removing the main injector the one in the center with 4 Phillips screwspull out the injector make sure the o rinon the end of the injector is good some times it takes some force to remove it after you get it out try some carbcleaner were the injector was removed there will be to small holes clean them out and use shop air after to make sure it is dry than reinstall the main injecter and see if it runs good just a thought.

Thank you for the reply. No check engine light. Performed the pressure check. It runs about 5psi at idle and drops slightly at full throttle.
We now suspect an injector issue. Spendy little devices.
Thank you Scott.

I read your problem is the check engine light on and if so is there any codes on computer as for checking the Nikki converter there is a nut on the top of the converter it has a Phillips screwdriver slot in the center this is were you check the pressure. make sure you turn lpg tank off and start truck let it run out of gas before you open test plug also becareful there is a small o ring on test plug do not loose it or it will leak propane when you install back in converter as for pressure you should see around 4to 5 psi when truck is running could see a little more with key on not running should not drop when running steady at 5 psi hope this helps