Hi again! ;)

i was wondering now that i think i have identified the problem of my car running too rich and slowly destroying the inner contents of the catalytic converter (again! it's really close to blowing the stuff out now, it's starting to not exhaust properly, mostly when idling - i am actually almost afraid of starting a fire or something) anyway, my new question is - what kind of repair do I need to make the car run less rich, a valve adjustment? I am just a little confused on what would fix it and i don't want to take this car to the dealer (1985 740 - they'll have a field day with it) without being able to SPECIFICALLY tell them what i want done. Or i may be able to go to joe shmo down the street that has done minor stuff on my car already but he's no volvo mechanic. I live in upstate NY and the closest place to get anything done on my car is Syracuse. What do i tell them so i don't get "raped" at the dealer?
thank you in advance, you guys are always so great :)

-volvogirl