how do the plugs look ?, pilots should be ok, im running 50's. but you being higher up could need maybe 42-45 pilots.
have you tried new plugs with the 270's ?
from 330 to 270 should be a big difference.
try some 260's. but check the plugs, make sure it isnt too lean.
pull the needles out, see where they are at. the needle should be a 5FP-17.
what are your air screws at ?
have you checked pick up gap and resistance, and checked coil ?