My '99 Outback has run great all summer. Towed it to a different lake and filled up on the way. When we hit the lake, the engine was running lousy, hesitating on acceleration, gagging when trying to hold speed, missing, etc. I pulled out the water seperating filter which looked shot (bad seal and rusting). Found the last one in town and replaced it. Ran OK for a while and then started hesitating on starts and you can hear the gaps in the engine tone at speed. I emptied it and reinstalled with the same result. I added Sea Foam and Heet to the tank over the weekend as well. Anything else I should look for? Thanks.