The motor upgrade was just the metal gearbox with whatever motors they came with - seem to have little more torque than the originals with the plastic gears. Speed 400's I'm sure would be better. I may try that myself. Although, the existing have plenty of power with the plastic tracks. I just came in from running mine and both tanks can climb very steep inclines. I have a hill from my front lawn down to the driveway about four feet long and 30 inches high - with grass - I hate that part of the yard when I mow, not easy at all. The Tiger's took that in stride - no stalls and the grass needs to be cut. I was very impressed. What kind of lubricant do you use on the gears?
I have a silicone lubricant which seems to be doing okay - don't know what the brand name it is though, but I have a lot of it.

The airsoft mechanism on my new tiger is very erratic shooting. The non-ss tiger is very consistent and accurate. I'Ve checked the barrel and the muzzel brake but can't see any obvious problems. It seems like the hop-up spins the bb sideways instead of up. I'm not familiar with these mechanisms so wouldn't know what to look for to correct it.

Are you using Nimh batteries? I have two 3600 Mah Nimh's but no charger for them. I want to get a quick charger but can't find one that specifies Nimh's. Well I did see a couple on the Tower page but they were very expensive - more than my tanks. I understand that the NiCad quick chargers won't work.