Puffing through exhaust

[2bobcats]

600 bobcat with vh4d wisconsin. Replaced both head gaskets because of excessive smoke.Torqued and retorted after running. Not smoking. Started up and after warming up starting traveling. Machine bogged down and died. When trying to start again it would sound like puffing through exhaust. I think an exhaust valve is hung up.Is there a way to figure out which one without taking heads off and without a compression tester. Thanks

 

[foton]

I guess if you had a helper you could pull out each spark plug and have them put their finger in the hole to see if it would blow it out or not, but why not just buy a tester so you will have a number figure you can go by.