V4 90/65 jet loss of power issue

Hoping for some advice here. Was having engine symptoms like running at half power not on all 4cylinders.(Johnson v4 90/65 jet) Took to local shop 4 new plugs timing adjustments and a new power pack. Was told power pack was cause of issues. Now runs well except i still get loss of power on full throttle. What happens is as i open up to full throttle it will run 100% power for always same amount of time like 1-2mins then it suddenly bogs almost like someone pinched a gas line doesn't stall but drops like half power. My way of getting buy is back to neutral then open up throttle again. Its an ongoing process and this happens only at full throttle if im 50% 75% it will run smooth all day long. can this be a sign of a bad coil or ignition wire? Im not losing gas prime i have checked this. Just looking for some advice and a few things can do myself hopefully to save a few bucks. Thanks for any advice.

Re: V4 90/65 jet loss of power issue

The first thing to do is a cyl drop test to see if you have some cyls not firing when the prob occurs. This can be done with an insulated pliers or a timing lite. If you have spark on all 4 the next thing to do is remove the air silencer cover and squirt some premix fuel in each carb throat and see if any cyl picks up. This has to be done when the mtr is acting up.