I also have a 99 RT with about the same milage. I've used platinum plugs since the first change at 15k. The correct gap IS .035. If it's off just a little then it can make a huge difference. I had one just a little shy (.028 or so) and it was missing badly while under heavy work (uphill driving) after regapping it worked fine. I have the Champion Double Platinum 7346 plugs. I wouldn't recommend the plugs with more than one electrode like the bosch 2 or plus 4 I've just heard too many bad things.
About code P1492 when I looked at alldata.com ($25 yearly subscription required for the good info) I found that this code is actually for "P-1492 AMBIENT/BATT TEMP SENSOR VOLTS TOO HIGH"
and gives this info:
SYMPTOM LIST
P-1492 AMBIENT/BATT TEMP SENSOR VOLTS TOO HIGH
TEST NOTE:
All symptoms listed above are diagnosed using the same tests. The title for the tests will be P-1492 AMBIENT/BATT TEMP SENSOR VOLTS TOO HIGH.
POSSIBLE CAUSES
BTS ground circuit open
P1492 BTS defective
P1493 BTS defective
Sensor signal circuit shorted to ground
BTS signal circuit open
BTS signal circuit short to voltage
BTS wiring harness intermittent defect
BTS wiring harness observable defect
P1492 PCM defective
P1493 PCM defective
If this is the code it has nothing to do with your problem.
You may want to try cleaning your combustion chamber (I've done it twice since my car was new). It's not hard to do, but takes an afternoon and a good stretch of road without cops (way too much smoke after cleaning). Change your oil and clean your spark plugs afterward. Don't be surprised if your car runs like crap right after you start it.
Here is the link to the info (BTW, neons.org is a great neon website for questions about your car-- these guys are pretty good with info).
http://neons.org/howtos/MoparCleaner.shtml
Good Luck.