I would not say the 8v has poor throttle response just no puff in the higher rev range.
In fact throttle response and initial torque is about all its got

It is likely you have a fault somewhere or are used to something lighter with a lot more power

Do you have a flat spot at around 3.5k?
Is the timing correct?
Is everything clean?
Have you got a cone filter sucking in warm air?
Lots of basic things make an 8v drive like a stricken trawler, best to be sure its all working before you go modding.
And I think 99% would agree the only thing to do for instant power in a Mk3 is to put 20vt engine in it.