My Volvo Pocket Book says the following about the history of the B6304 engines here in the US.

to 1994, .. HP 204/6,000 rpm, TQ 197/4,300 rpm, C.R. 10.7:1
1995 only, HP 181/5,200 rpm, TQ 199/4,100 rpm. C.R. 10.7:1
1996 up, .. HP 181/5,200 rpm, TQ 202/4,350 rpm. C.R. 10.7:1

O.K. We know that Volvo changed the camshaft specs for the 1995 model year to produce the changes we see above. (The HP and TQ curves are quite different which produce a very different feel than one would expect by just looking at the numbers above.)

1) Did they change anything else for the 1995 model year in the engine besides the cam grind?

2) What did they change in model year 1996 to obtain the change in torque. They went from OBDI to OBDII in 1996, could that be responsible for the change in TQ numbers? (for example : more efficient control of the engine, as in... a second o2 sensor... thus better ECM control, that sort of thing?

DEWFPO

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1998 S90 066,800 and 1995 964 150,200