If you had bad rings you would have a blueish smoke coming out your exhaust. This would happen most of the time. It doesnt sound like that is your problem. If you go to Autozone they will lend you a compression tester for free. All you have to do is put a deposit down untill you return it. they now do that with all automotive tools. If you have good compression and want to fix the problem a dyno with A/F readings is your best bet.