[rodeo02]

1) I've never seen a fuel tank additive capable of clearing out clogged EGR plumbing. Some fuel system additives will reduce carbon build-up, but once the additive is combusted in the engine, it looses most of it's cleaning ability. Seafoam is good stuff, but a cheap $1/can spray carb/intake cleaner will work just as well if you have the EGR valve removed.

2) I dont know the number of drive cycles needed to clear that EVAP system malfunction code, but is usually quite high, like 25-100 full warm-up & drive cycles. This could be just a stuck check valve in the gas cap allowing tank press to bleed off. Make sure you can just suck air thu and not blow air out of the gas cap (neighbors love this maneuver). Does the '99 have a check gas cap light? (a little gas cap icon).

G/luck
Joel