Hoping I can find someone who has run across this problem before. I have a Fortis Hyster H50FT L177B18683E with a 2.2L Mazda LPG engine. This lift has a problem that, one has been difficult to catch, and two is not very consistent. The customer called and said the unit was running rough and would die when he drove it across his warehouse floor and let up on it. When I got there the unit ran perfectly! No issues, no error codes, nothing. I ran the unit for about an hour and it was running perfectly. I left that night and decided to come back in the morning,maybe when it was cold it acted up. Got there in the morning and it started right up, ran great for about 20 minutes then when I let off the gas pedal it died. Tried to start it and it started right back up and ran fine again. This same scenario happened about 4 more times off and on. No dash codes and it happens so quickly and fixes its self so quickly I couldn't test any components. I since have picked the unit up and brought it to our shop it has been two weeks now, starting and running it every day and it may act up once every other day or every third day. It will rarely but sometimes does sputter upon start up but comes out of it right away. We have tuned the unit up, replaced the fuel regulator, ran a new fuel line from the tank coupler straight to the LP regulator, cleaned the grounds on the truck, but it still will act up from time to time. Anyone have any ideas? Your help would be much appreciated.