easy..if you havent done it already replace all the ignition componants that wear (dizzy cap, rotor arm, leads, sparks)
now replace the filters (air/fuel)
now take it to a GOOD garage with a crypton tuner and get them to set it up...(tell them to hell with econamy you want performance)

wana bet you notice the difference...if not you have jsut done a load of preventative maintenance anyway...

after that rejetting the carb (or swapping it for something a little 'throtier' & exhausts etc are next...) - for this you need to find someone who knows what they are doing as the engine will need tuning for the changes and in parcicular the jetting will need playing with....

please please please bear in mind a 700 is never going to be a sports car it just weighs to damn much!...i would also suggest that if you want one that goes you seriously think about a 700 or 900 turbo - in reality buying one a stock one will probably give you more bang for your buck$ than a 700 na will without MAJOUR work that will be more expensive than buying & running a turbo...

even a 900 turbo isnt exactly majourly fast...it just sort of surges and leave stuff standing (dont buy the I turned my 940 turbo into a porshe eater brigade - possibly in a straight line but never through the bends! - well not without a space frame anyway!)

look at the figures...a 900 turbo just about lives with a 1.8 vectra ls...