Engine problem

Lowrance

Lowrance

Hi the problem is when the engine heats up then it works sometimes on low gear, below 1000, however, sometimes it works above 1700 - as if it sucks. generaly, it has its ups and downs. nevertheless, i've got a feeling, that it depends on the fuel-mixture - to rich or to lean. Fi doesn't work [glow], i've done the syncronization, all the contacts are greased. i've got the most problems when the engine cools off then it pulls and stops. i've changed the fuel, udes some cleaning liquids, new spark plugs, air and fuel filters.. and nothing works. HELP!