I have a 262 which also has the fuel injection system.
First, check that the fuel pump fuse(s) fit tightly in their holders. Silly I know, but all sorts of nonsense can be caused by 'wobbly' fuses. After that, my next thought would be the fuel pump relay as if this is faulty, it causes pops and bangs and weird things like you describe; followed by the auxilliary air valve that might be sticky?
Unless of course it's something else. But none of the above are difficult to look at. If you need a source for low cost bits; a scrapyard where you take them off yourself or, especially for a new fuel pump relay, try the lot on the link below: they have them for about £10 whereas Volvo want about £40!
http://www.volvoparts-uk.co.uk/contact.htm
They are:-
North West Motor Trading (Tel: 01942 887800 )
Riverside Mews
North Road
Atherton
Manchester
M46 0RF
Just 5 minutes from junction 5 off the M61
Regards
Andy