ASV Power Issue

Hi all, I would appreciate your help. i have recently purchased an ASV RC30 knowing there were issues. Originally the drive would get lazy on the left when hot. Long story, but I tracked this down to a missing o-ring in the left motor. I have had both motors apart and put a seal kit through them. No obvious wear in the rotating element. After fixing this and lots of other small issues, i finally have it working. I have used it all weekend and generally it seems ok. The original problem that would happen after 20 mins work has gone. But the problem is i have never driven one before and think it is lacking power (but have nothing to compare it to). I find that i am always running this at full revs or close to it. Is this normal? Also at home i have a small very steep section. I struggle to get up it. It is mildly worse when hot and if loaded it wont go up at all. The motor doesn't stall, it just stops moving. if i try to turn the machine part way up the bank it wont go anywhere. I have a test gauge on the pilot pressure and when this issues happens the pressure drops, so i assume oil is bypassing somewhere (it is the same forwards and reverse) I am wondering is the drive pressure relief valves are opening early? But i thought if this were the issue it would only happen in one direction (forwards or reverse) I am planning to test the drive pressure but any other advise, ideas from someone who has seen this before would be appreciated. Regards GM