What are the symptoms of bad timing in a 1998 Cavalier?

I have a 1998 Chevy Cavalier. A while back, the fuel pump went out and I replaced it. It ran fine for about 10 days but then started to run horrible. It still ran, but it took a while to start would stay idling in park and neutral, but when I put it in drive it would die unless I was giving it gas. However, if I gave it too much gas it would start to stall. I ended up getting new plugs and wires, coils, MAP sensor, crank position sensor, throttle position sensor, idle air control valve, and fuel filter. None of this worked, so I got a new fuel pump and put it in and it ran good for 3 days. Then all of the sudden, the symptoms reappeared. It would still run but I had to keep giving it gas. Now it'll start but not stay running. I've heard differing opinions. Some people say it's still a bad fuel pump (I bought the pumps cheap on ebay). I was getting ready to just replace the pump and embly this time, but now others are saying it's a timing issue. What confuses me is that it runs fine for several days and then the symptoms come back. I hope someone can help. I really don't want to sink too much more into it. It has been a nightmare lol.