Tecumseh tvn220 ?

I have a tvm-220 10 hp engine on snapper mower,starts up runs good sitting there,under load engine will almost shut down at times under load.Things ive done,cleaned carb,new kit 2 years ago.Ive tried adjusting carb.several times but after few minutes it will do it again,this is just under load.will run in shop all day.have this as 2nd mower just in case but hardly gets used.Sure it,s gotta be something with carb,but im missing something.by the way always keep fuel treatment in gas and only put any in it in spring just to run it a bit.Sometimes it will run around field and not miss a beat till i turn blades on.any ideas?Paul

Google: Tecumseh engine service repair manuals, see if it helps.