Several problems with '99, please help!!

First off, I've been trolling the forum and have seen some other topics that are similar, but no clear answers. So, I thought I'd start with a fresh post.

I'm having several problems with my '99 ES. I've got just over 140k freeway miles, so I guess it's time. I'll just list them in order:

1 - The worst problem is that it's stalling. It seems to usually be when I stop at a light or the rpm drops quickly. It starts right back up.

2 - My fuel guage and light is off about a 1/4 tank. It doesn't go up all the way and the light comes on way early.

3 - Oil light comes on when I'm on a slope going upwards. The oil is definitely full. I saw another post mentioning the timing belt. JFYI, I had the timing belt changed within the last 6 months. I DO NOT recall the oil light issue before the timing belt was changed.

4 - I get a very nasty pinging noise that sounds like it's coming from under the injector cover. It speeds up when I accelerate and is most noticable when idling. I've seen references that this may be the lifters, but not sure.

If anyone has a good idea of what these problems may be as well as how to fix them, please let me know :)

Thanks!

Regarding your stalling:
If you havent replaced your PCV valve in a while, try that. If that doesnt fix it, your problem is most likely your EGR valve. You would want a new PCV valve upon an EGR change, anyways, so try that first