A standard G40 has its top speed at 122 and I doubt (considering how much has already been done on a G40 engine) it would be much more with some modifications. A porsche in any guise is an extremely quick car and that can't be doubted and some of the best fun on four wheels (Or so I am told, won't be able to drive one of those for a long time yet!).
Looking on the net, a well driven Porsche 911 can be in the late 10's (with mods) or the mid 11's. Not that I know much about 1/4 "racing". That Fiat 126 weighs less than most cars on the road and has a large engine, hence what seems like a mad speed, which it is for a 126...lol! However, you try racing the two and the 126 would be a lap down after 2 IMO.
A porsche is a supercar, a G40 and type R are toys in comparison. It might not be the fatest thing on four wheels but it is still one of the best!
Paul
My first signiture (a lot of thought put into it): If you can't find the switch to switch your fogs off I am sure I can help you! Damn fogs.