Okay, 200+20=220 makes sense.
The Gr.B is based on the TA64 GT-TS but the Gr.B rules allow further changes (eg extra radiator).
Factory race cars go through a similar homologation process here in Australia.
The factory makes a model with some of the interesting stuff already on the car that the rules say can not change (eg engine block).
But if the rules allow something to be changed (eg wheels) then the road car has just ordinary items.
The race team will change those things for better ones.
Here is a press release from Toyota Great Britain.
http://www.toyotagb-press.co.uk/prot...caTwin-Cam.htm
Here is at least one TA64 road version that has been made into a rally replica (near bottom of page, after RA63)
http://www2s.biglobe.ne.jp/~gtr/celica.html
- Stepho