Do you know the history of the car, these engines do not take kindly to neglect and will explain the tapping your getting, also if someone has used the wrong oil this can cause problems the correct oil is what you have replenished with.

It really is difficult to know what you quantify as slow, maybe you are expecting to much?

From experience the MK1 is fairly nippy don't see why the 2 should be any different.

That rattely noise is also common you talk of.

Martin