Updates please after your ride a bit with the new baffles! Ill be curious to see how you get on...
Ive never had a problem running at altitude on my K4 (since it is running rich already I guess this is the reason) - usually though it was only passing through somewhere but...riding from LA to Grand Canyon (at 7000 ft) then to Colorado (10,000 feet passes) I never felt like the bike ran poorly. Also when riding through Mexicos Central Highlands (6500 ft) after having come from the coast - again no issues...and when I went to the Alps and passed through some 10,500ft passes no problems....
I was running a combination of Mac 4-2 (Mexico trip), aftermarket 4-4 (Alps) and stock 4-4 pipes for X-USA trips...all at 110 main jets, stock airbox, stock filter....never played with the needle clip position but think its in stock position (2nd clip?). Maybe your older 71 is a little more temperamental.
Anyway good luck with it.
cheers
Andy