Hows it going guys so i have a 02 trans am with pretty much stock everything except the 243 heads and gutted the cats. Now heres whats going on i did a compression Test and it only reached 30 and if i leave it on for about a min it leaks down to zero iv tried on the other cyl and all stayed at 150 i dont have a leak down tester so any ideas to tell if its a valve or rings. Also when i drive and shift it back fires now any advice will be appreciated

 

Plugs look great just have some oil on threads

 

Backfiring out of the exhaust or into the intake? If it were rings you would probably see more blowby than usual.
Although you don't have a leak down tester you might be able to use your compression tester if it's the screw in type to pressurize the cylinder if you can scrounge the fittings.
Put the cylinder in question at tdc of the compression stroke and pump some pressure into it and listen for leaks.

 

It backfires threw the exhaust every time i shift and it doesnt smoke at all unless im down shifting to engine brake and even then its very minimal

 

I pressurized the cylinder at tdc not sure if it was the compression stroke. Or not but the only leak. I could hear came threw the oil cap

 

No one else?

 

Holy run-on sentence. You can carefully look at your closed valve heights to see if a bent valve is keeping it from seating all the way.

 

Put a couple squirts of oil in the bad cylinder and retest compression. If it build compression, whether it leaks down or not, that would generally indicate rings. If it still doesn't build compression, that generally indicates valves