Need help...CV ain't runnin' right!

It just started here lately. I start it up & if I don't keep my foot on the gas, it dies...even after it gets warmed up.
The check engine light's on, but it seems to do that every once in a while...it goes off on its' own & pops back on at the darndest times. This time, tho, it's stayed on. I haven't taken it to AutoZone to see what the deal is. Last couple of times it was something about the catlytic convertor or something.
Has anyone had a similar problem to this? I put a can of seafoam thru the pcv, but it didn't seem to help so far...just a smoke show.

What model year?

Sounds like the catalytic is plugged. Does it run kinda sluggish?

It's a 98 CVPI...it seems to run fair...don't get on it much due to the cost of fuel...hehe.
Where's the fuel filter on this puppy at, btw?

i believe the fuel filter is behind driver side rear tire... it should run close to the exhaust

Post back when you have the trouble codes read. Post the exact number, not what the person tells you is wrong.

OK...I stopped by AutoZone today on the way home to get a can of Seafoam to put in the gas tank. I also inquired about an ICR (?) but I don't think what they showed me on the computer was what I wanted ($161?).
I had them bring that handy-dandy code reader out to the car & it showed 2 codes...a PO442 & a PO420.
Does this help?
I think one of them has to do w/the catalyst...I think the code reader said something about not performing up to snuff or something. They also mentioned something about a loose gas cap (got a new, locking one) or some kind of charcoal cannister thing. I dunno.
Any help would be appreciated.

**UPDATE** I smacked the ICR some after I read an article online, but it still did the same thing this morning. On my way to work, it stalled when I pulled into the convenience store. After I got off work, it started fine, idled fine & on the way home, the check engine light went off. When I pulled into the drive, it was still idling fine. Go figger.