A few tips for you:

1. I would encourage removing the accordian tube between the throttle body and the Air Mass Meter. Clean it out, and bend it around while inspecting for hairline cracks. -you're probably going to find a few where the accordian tube has been rubbing against the fender wall or the battery cable. Get the tube as clean as possible, and then wrap it in electrical tape (use a lot) until you can get a replacement tube.

2. It sounds like you may be overdue for an O2 sensor change. This will easily pay for itself in a few months with increased fuel mileage. Check out the following page for cheap 3-wire Bosch sensors that can be used in your Volvo: Bosch #13913 and #13953. Don't discount the importance of this sensor, it's 2nd in command of your fuel mixture (behind the AMM).

3. Check your engine for vaccum leaks. Verify that the two tubes from the charcoal canister to the throttle body are properly attached and not cracked, -and also the vacuum tubes at the intake manifold near the flame trap. Also check the Fuel Pressure Regulator vacuum line. A cracked or split vaccum line will allow extra air to enter the engine and lean out the mixture.

4. Get a good set of spark plugs. The best that you can get are the official Volvo ones from your local dealership or FCP Groton. They cost $11 for a blister pack of 4 plugs ($9 at FCP), and are superior quality than anything else you'll be able to find. If you can't get the OEM Volvo plugs, NGKs are a suitable backup, and the Bosch Super (copper) plugs would be 3rd in line. Do not use Platinum plugs in your Volvo since the ignition system is not designed for the higher impedance of a Platinum plug. (there are service buletins that cover this topic)

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 246k miles.
'88 Black 780, PRV-6, 145k miles.