96 2.4L sometimes rough when accelerating

I have a 96 2.4L that sometimes has problems when accelerating. I took it to my local shop and they spent two days on it and couldn't find the problem. They replaced fuel filter, did a complete tune up, checked fuel pressure, cleaned and checked injectors and all emision systems. They suggested maybe sticky lifters so I added a can of the stuff you add to your oil and let it run for 5 minutes then change your oil. It ran okay for a few days and does seem to run better but still has problems. After it warms up it idles a little rough and there is a light pop pop from the exhaust.

Two words: Head Gasket.

Two words: Head Gasket.
Ouch! That sounds expensive. This morning it ran fine on the way in. The check engine and ets lights were on when I started out but went out mid way here. It was idling fine but I know it will come back!