I have an engine issue I would like opinions on. It is a Continental Packette, I have two week cylinders that are blowing back through the intake. I tried staking the valves to no effect, I checked clearance on rockers. I can pry out on the valve spring to increase closing pressure and get them to seal up better, not perfect but better. What are your thoughts?

Run it hard for 30 min and do a hot compression test. Boroscope the valves. Does it have any issues that are noticeable while it's running? Running a genset? Can also try a valvelap procedure if boroscope doesn't show any chipped valves . Really nothing to loose.

Bore scope it, wobble test the valve and lap the valve.

Ok I surrender,

"Bore scope it, wobble test the valve and lap the valve."

What is this test, is it for valve stem/valve guide slop ?

Yes, wobble test is to see how much side movement you have between the valve stem and the valve guide, actually simple test to do.