My DD '98 Sebring has been throwing an EVAP leak code for a few months now. The engine has also been running not quite right at low speeds, like under 15 mph with very light throttle for longer, kind of surging, like a vacuum leak. I assumed this was the EGR valve going and I just didn't feel like replacing it yet because the car still runs fine everywhere else but my driveway or a parking lot.

Lately the 'surging' has been creeping up in the RPM range. I've been reading that the EVAP leak won't cause driveability issues, but I've also been getting crap fuel mileage. The first tank I figured it was a combination of short trips and cold weather, but the fuel mileage has been getting consistently worse, and this last tank was mostly highway miles.

I suspect the poor fuel mileage may be related to the engine 'surging', or it could be related to a recent exhaust leak if it's before the O2 sensor, or it could just be from really crappy gas, I don't know.
Would the EVAP leak cause the 'surging' and drop in fuel economy? Is the EGR valve part of the EVAP system? Would the exhaust leak cause these problems (it's kind of big)?

No hurry to figure it out, I just had time today and thought I'd try to figure it out.

p0442 EVAP leak small
p0455 EVAP Leak Detected (no purge flow or large leak)

My 01 Grand Cherokee with a 4.0 has had that code for over a year and I haven't noticed any problems except the check engine light stays on. Also have been driving my brother in laws 4 runner on which the gas cap is missing and I can't tell any difference from before the cap was lost. Hope this helps.

EGR is not part of the Evap. The Leak could cause a drivability issue if you have a vac leak from the intake to the purge solenoid supply or the purge is stuck open. Plug off the hose to the purge solenoid and see what happens.