Anyone with a DC5R ever experience a decrease in performance where you thought it may have been the clutch but however replaced the clutch and noticed it still isn't as it use to be.

The car has 135kms on it. Clutch is like new only a couple of months old.
Now when trying to 'fang' it on second gear for instance it doesn't accelerate as quick as it use to. Much slower actually.

Would anyone have any idea what this could be? Timing belt maybe?
Any help is appreciated. Ta.