Deceleration speed in 2.6lt Bravo

I have a Mazda Bravo (B2600) 2.6 petrol. When I push in the clutch to up change through the gears, it takes an abnormally long time for the revs to die down. I either have to wait or force the gears through which is not good. I recall years ago there was a thingy (a dashpot I think) which could be adjusted but I don't see an obvious adjustment point on this vehicle. Any help is appreciated Fellers,
Thanks,
Harry