29-07-15, 05:45 PM
There aren't many things left that can stop it revving under load yet not affect it off load.
Partial blockage of the fuel or air supply may still be possibilities.
Poor compression often makes starting difficult, but is worth checking.
The only electrical thing I can think of and may not have been changed is the TPS, though I don't know if that can fail in such a way as to limit the revs that severely.