1991 Beat engine problem
 

Hi, I have a 1991 Beat PP-1, it has some problems. Firstly, as known, an E07A MTREC has max pwr @8100rpm, and cut off @8600, I did rev it to 8600 too, but more often I found it cut before these, sometimes 8000, sometimes 7600, sometimes 7200, even 6800, how could it be? What's failing?
Engine is not overheating, battery is new(Panasonic), lubricant,spark are new.
Fuel using is 98(only type of petrol in Hong Kong, we don't have 92,95).

Secondly, I found my car cannot start when it's warm, I need to step down the throttle pedal when key is turning, cold starting is perfect, wonder what is not working when warm.

Air -con is cold, although I seldom use it, as Beat