Besides slow revving, did the car idle smooth and produced power (albeit low) in a linear fashion?I have had 2 cars now that would not rev up.
One was a 5008 ep6 turbo with no fault codes.
0 - 60 in 3min it was that bad.
Timing was out on both cams.
There is only a sensor on intake cam so it did not put light on because it was in an acceptable range on intake side.
Euroserve stated timing system check will be next port of call.