Phewwww....mate, you've been trying for 4 months now to get it running and if the guys in the shop can't get it to run either then they should have replaced it immediately for you. Admittedly they don't seem to have many clues going by the fuels they recommended you use...sheesh, an Aussie saying to use 20% nitro?...and in a Super Tigre? They must have a good mark up on their high nitro stuff . I use zero nitro in all my engines including several ST's (ABC and ringed) and they run perfectly on it. Go tell them enough's enough and don't get talked into buying an overpriced OS .