Stalls when at working temperature

You definitely need to get your timing light out and hook it up and my guess would be that your timing is advanced a little too much.

This is usually a problem caused by a bad water temperature sensor. There are usually 2 sensors with one working the temperature gauge and the second working engine controls.

The "cold start" sequence is similar to a choke in old cars. It needs the signal from the water sensor to trigger the cold start sequence. The cold start sequence enriches the fuel charge, adjusts timing, and increases idle speed until the engine gets a little warm.

Now if stalling when warm, you have other issues. Manifold runners are a problem on some engines.

You need to run a fault code test as a starting point. Learn how to do that here

it will have codes but the scanner in use doesn't have the right protocol for reading them
Indicates a faulty ambient air temp or BARO sensor so there will be codes

Possible CTS or coolant temperature sensor if improper temperature is being sent to the computer for fuel and air delivery as controlled by the computer.

its rooted sell it to the breakers

Mileage on timing belt, depends on year ? make (volvo) model (c70) and engine size?. heres a couple of mileage readings,the 1998 c70 with a 2.3 turbo engine is due every 70,000 miles. the 1999 -2001 c70 with 2.3 turbo is due every 105,000 miles. the 2002- 2004 c70 with the 2.3 engine is also at 105,000. the 1998 c70 with the 2.4 engine is due every 70,000 miles. the 1999-2001 c70 with the 2.4 engine is due every 105,000 miles. the 2002- 2004 c70 with the 2.4 engine is due every 105,000 miles. god luck hope this helps.

You have a slight leak from one of the hose connections going to the heater core.Yes you can do it yourself.Check it out.

BATTERY CONNECTIONS ARE CLEAN AND TIGHT?? CABLES ARE TIGHT AT THE ENGINE. AND GROUNDED AT GROUND STRAP???