For starters, try tuning at 1/2 tank. Run the 1st half tank then tune the motor. Refill and see how it performs. My Savage LE had this issue really bad. I was seeing swings of 50 degrees and more from full to empty. That also caused it to run like total crap until my tank was 1/3 or so empty. Try tuning at 1/2 tank first and see if it works for you. Aparently most people don't have the problem as bad as I did. But, if you rule out tuning at half tank and make sure there are no air leaks, then you can buy the kit from New Era to fix your problem. It does cut down on your run time, but it all but completely fixed my problems. Here is a link to the kit I bought:
http://www.neweramodels.com/cgi-bin/...b&part_id=1704
The tank they sell in the kit is a 125cc Ofna tank that you can get at Towers for about $10. But they also included aluminum mounting hardware to mount the tank since the stock parts will not work with this tank.