If no check engine light and no codes to go by - then maybe big spring tune up is the right thing. Change all filters - gas, oil & air. If non-turbo change flame trap. Does gas pedel seem a little sticky? You'll likely find a dirty throtle throat - you need to disconnect air hose coming from air filter to do this. I've also noticed that after 40k miles on a distributer/rotor performance declines. And don't forget the spark plugs! They also don't like more then 30-40k on them.

For the A/C try a home recharge kit first or have some do recharge (with dye). You can spend big money to replace A/C parts or just recharge. I got almost 2 years on my '94 with the last recharge - cost of recharge kit $30 (includes coolent, connector & presure gauge). I also have a '93 that has not needed recharging in the year I've had it.

And after all that you'll probably find a leak in a vacuum line.

For a great site on maintenance check out Bay 13 at: http://www.volvospeed.com/maintence.htm

Good Luck!