Did some compairing levels 4 and 6 today on the ez. Pulling a trailer of only about 5k (enclosed tandem). Level 6 was slightly more responsive, not to noticeable though. Normal cruising egts at 75 are the same as stock on both settings. Then we compared the 2 settings with the g-tech while watching egt's. Level 4 was 0-60 in 8 sec and quarter was 16. 3 @ 88mph and egt peaked at 1250 around 85 and then started dropping. Level 6 was 0-60 in 7. 6 and quarter went by in 15. 8 @ 91mph and egt peaked about 1375 around 85 and then dropped off to around 1200. To answer you question about level 4, catcracker no, I don't think you will be disappointed at all with level 4. But as you can see level 6 does indeed have a few more ponies!