2002 Saturn Vue Not starting, flooding engine

Hi, my Saturn Vue is not starting and is flooding my engine with gas. My mechanic is at his wits end figuring this out. His analyzer isn't coming up with anything. Compression test is good. Injectors appear to be good. When it started I had made a trip a couple hours away that normally takes a half-tank of gas but this time took the whole tank and the ride was a little rough, seemed like it was "choking" for the lack of a better word. This gradually got worse before taking it to my mechanic. We thought we fixed it a couple time. Replaced an O2 sensor, started right up like normal. Next day it was bad again. He replaced the engine cooling sensor, again started normal but was bad again by the time I went to pick it up. Although it's fewer and farther between there have been times when it still starts perfectly normal without any reason why. Sometimes it'll start somewhat normal and then you give it gas and it just drowns out. Sometimes it won't start at all. He's down to thinking it the computer, but not completely positive and that's awfully expensive if it's not it. I work on computers for a living, so I don't speak "car", but if it's the computer usually computers that aren't working because of a component always don't work, there's not usually a time when it works fine. I hope I've given enough details because I sure could use some help.