Never had much success cleaning these injectors. Usually results in replacing it. If it stumbles and cuts out, that is the most likely culprit. Some have cleaned these injectors and made them work but i have had no success.

RCAV8TOR, Thank you for the reply. I called the customer and discussed the possibilities of resolving his lifts issues. I suggested cleaning the fuel system (injectors, throttle body, last chance screen) and fixing the brake switch. He wanted to wait as he did not have the budget to pay me. If and when I do go back, I will definitely come back and let you know what I find. I have a strong suspicion that the fuel system is the culprit. Again thank you for a shove in a direction.

Well lets start with the e-41......Install new brake /stop switch. This will require clearing the code again. Now lets look at the half throttle issue. E-41 should not make lift do the half throttle thingy. Is or has lifts speed been reduced ( set speed lowered)? To check this is as simple as starting unit and in neutral, go wide open throttle and gently dead head hydraulics (tilt backwards untill unit labors). Does lift rpm drop or does unit try to compensate for dead head? If not then you have a fuel pressure issue. Here is where laptop and software would be a plus but you can do some obvious checks. Check the transmission overheat sensor located on transmission ( 1 wire female connector) and clean it or make sure it isnt grounded to frame. Check final chance filter located beneath LPG pressure sensor ( black thing secured with 2 screws on top of injector holder). If dirty, use carb cleaner to flush screen but dont remove screen and use light compressed air to blow out. Did you by chance disconnect battery with key switch on? If so cut switch on and off.......wait 10 seconds and restart unit. Was it wet or had been run outside in water that day? if so check tranny overheat sensor as listed above. Let us know what you find.