i was offered a set of bbs e88 from another member. will this fit on a 993tt?

Here are the specs:
Front: 18x9 44mm Offset
Outer rim 1.5 in.
Inner rim 7.50 in.

Rear: 18x11.5 44mm Offset
Outer rim 3.0 in.
Inner rim 8.5 in.

 

i my opinion, a very tight fit , both front and rear - you should be able to judge for yourself by making an offset diagram and comparing with what you are running on the car now.