After looking back for the info it seems that some of the 02A passat boxes had a higher (or is it lower) final drive in them but a different set of ratios. So a straight swop won't give you the desired effect.
Changing the final drive will increase your pulling away speed in first, and lower your overall speed in each gear. It will also lower the mph gap between each gear. In theory then for the same speed in the same gear you will be higher up the rev range with a higher final drive.
You can achieve similar results by going to lower profile tyres. If you are running 195 /50/ 15's then you could try running 195 / 45 /15's.
Don't shoot me if I've got the higher or lower the wrong way round on the final drive. A standard 02A Mk3 16v box has a final drive of 3.64 ish and you want to swop to a 3.9 ish one or go all the way and swop to a 4.24 ish one.
The 16v box has a very long third gear. If you were going the whole hog then you really need to change the final drive and some of the gear ratios.
I believe Glen (Ess Three) has done this.
Paul