Johnson 140 v4 two stroke

[Johnson 140]

hi new to the forum,ive got a johnson 140 v4 two stroke 1983 to 1985 model still in very good condition .Can anyone advise me on the following .

Coil packs - must it have a single coil packs or can dual coil packs be put on ?
reason for asking because the motor stutters at takeoff
Carburetors - ive recently had my carbs been replaced but now much less performance ,the barrels measures 30 millimeters and the previous was definitely bigger

ANY info on this engine please do reply