As for revving up: Three possibilities.
1. Diaphram in rear of injector pump losing seal.
2. Line from diaphram to butterfly valve on right side engine leaking vacuum. Vacuum induction on right side engine leaking
3. Rings worn to point of crankcase sucking or rings cracked from ether.
Diaphram is EZ to replace. Pneumatic govenor piping back to air induction is basic. Since you state it was at high RPMs, I'd suspect # 1 if it is constant and predictable and #3 if hard to start, acts up only when warm, and oil level drops after use.