I have four questions, myself:

1) Has the mechanic checked IP timing?
2) Has the mechanic checked for chain elongation?
3) Has the mechanic checked for boost and for a functioning ALDA?
4) Has the mechanic checked to be sure the throttle linkage is adjusted properly and is fully opening the rack on the IP?

Ask the "mechanic" these four questions.

If you get a stupid look out of him...........immediately remove the vehicle from the premises.

The problem is almost never the IP.