Here's the skinny on the changes to the 960's engine, from Volvo's site:

1994 960:
Horsepower (SAE net): 201 @ 6000 rpm
Torque (ft./lbs., SAE net): 197 @ 4300 rpm

1995 960:
Horsepower (SAE net): 181 @ 5200 rpm
Torque (ft./lbs., SAE net): 199 @ 4100 rpm

As you can see the camshaft change increased torque and moved the peak hp and peak torque to a lower RPM, effectively increasing available power at normal highway speeds. Never having driven either model years I can't how much difference there is, but there are other reasons that would make me choose a '97 or '98 over earlier years: the durability of the timing belt was improved in the '95 year to give a 70k mile interval, and the more durable the timing belt the better IMO! However, a fair number of 960s in '95 and '96 had problems in the casting process for the block that resulted in porous engine blocks, bad news and almost impossible to repair. Therefore, if it was me and I was set on having the 6-cylinder I'd look for a '97 960 or a '98 V90 (same car). But as other posters have said, the '94 and '95 940 turbo wagons are also excellent cars, cheaper to maintain, and cheaper to buy. Look at both and see which one you like best.

jeff daigle
'89 745GL 136,000mi