I have an RB30 patrol and this weekend I have experienced similar issues as you described, where the engine would drop revs and stall if I put the clutch in and let the revs fall and wouldn't idle. It also did the backfire when going down the hill as you described, what did the problem turn out to be?

Any help would be greatly appreciated, right now it's running fine again, it just seemed to happen for a while then go away again, then come back at random.

Thanks, I was ready to park it in the lake yesterday it was winding me up that badly...