I'm having some troubles with intonation on my new(used) Kanstul 1500 in lacquer. My ear and the tuner(for once) agree. Middle G is particularly troublesome(sharp) but there are several notes on the horn that don't sit particularly well. I'm adjusting all the time while playing. It seem to be in fairly good repair except there is evidence of red rot on the leadpipe and tuning slide. It's not terrible but it's certainly there. Would a new pipe do anything to help? Any recommendations? Blackburn, Pilkzuk, etc.?