1996 Mitsubishi FTO intermittent engine surge

Hi there.

my car has an intermittent engine surge or misfire and I can't track down where its from or why it's happening. The symptoms are:

1.) The engine will only surge when the revs are between 0-2200rpm

2.) It will only surge occassionally once the engine has warmed to operating temperature - not when it's cold

3.) It will not surge when the air conditioning is on

4.) It will only surge when driving at a constant speed (0-65kmph), not while accelerating.

5.) It surges throughout all 5 gears, just so long as its within the rev threshold of 0-2200 approx.

6.) It does not surge at idle, only in gear and when driving

at higher speeds the engine is completely normal. The surge itself is just a very quick and very momentary loss of power.
I have changed spark plugs, and air filter, as well as spark plug leads. I will be replacing fuel filter asap.

Please, any help will be very much appretiated!


Kyle