[mylesdw]

I think the choice is: with or without vacuum advance. You need the mechanical advance or the performance would be REALLY bad.

Vacuum advance makes no difference to WOT performance but it effects fuel economy at part throttle. When cruising around you will use less petrol with vacuum advance hooked up.

My car has no vacuum advance and I intend to change that one day. If you have the choice now, take the vacuum.

Hope this helps