I had the same problem when i bought my 1980 242GT, this may apply to your car if it has been sitting for a while (ive talked to many mechanics and they say that problem it is very common for cars that have been sitting), what could be the problem is that inside the fuel distributer there is a pin that moves up and down with the air flap and regulates the flow of gas. When a car has been sitting for an extended period of time the pin can seize up therefore making the gas stay full out, even when u arent pressing the gas pedal. My car had this problem and it would run if i kept the gas pedal a little on but as soon as i let go it died.
Whats happening is that because the gas is coming full on, and by feathering the gas pedal(like your friend said he had to do) it opens the air flap so that there is just enough air to compensate for all the gas.

Some symptoms to look for are: after cranking it for a bit 1)remove the large rubber boot held on by hose clamps that goes from the throttle body to the intake manifold, if there is gas inside then u most likely have the same problem 2) also ask your friend if when it ran it smoked a lot which can be the result of running rich 3) another thing to try is crank it for a bit, then pull out the fuel pump relay (this starves the engine) and it may start but it will not run very well.

advice:
a good idea is to probably just go down to a junker and pull a whole throttle body off of a car with your same engine and injection system(your engine is probably a b21F engine with k-jet injection), the fuel distributers are often to hard to get off the throttle body and removing them can actaully ruin it. Make sure u get the right model, look for the serial number on the fuel distributer, the fuel distributer is a dark boxy thing with a bunch of hoses coming off of it located directly under the intake manifold and it is towards cylinder 4. the serial number will most likely be on a purple rectangular metal plate and for the b21F engine the serial number is 0 438 100 023. The throttle body is not to hard to install but if your unsure about it get a shop to do it. If you do it yourself its a good way to get to know your car, i have not had any previous mechanical experiance and i completed this job in around 2 hrs.

things you will need to do this job:
1) new throttle body (i got mine for $14.00 canadian)
2) New intake gasket (you will have to undo the intake manifold to get the fuel distributer in and out of the car ($6.00 Canadian)
3) gasket seal ($7.00 canadian and your local auto store)

Note:*Also this problem can appear to be the cold start injector flooding the engine to rule out the cold start injector just simple unplug it (shown in most repair manuals)

If you need more help feel free to post a message on my community i will be sure to get back to u http://groups.msn.com/SoupedSportVolvos
Hope this helps

VoLvO_4_LiFe