believe it or not, but i just went through that with my os.18 last week. i had the same exact problem. here's what i did, i ended up going back to factory settings, i think 1.5-2 turns in on the low side and 2 out on the high side. then i didn't adjust much more from there. i think i just did the high speed. and it was very little turns like you said. i also tightened my slipper and adjusted my shift point. it's funny, but it was exactly the same problem. oh and i think what helped the most was i turned my idle up a little more then what i thought was normal. it absolutely screams now and sounds great. it's running at about 245, but now i blew out my rear diff so i haven't been able to drive it for a couple of days. it took me about 2-3 days to tune it, but i finally got it. good luck.