Groups question

I didn't want to revive an old thread, so thought I'd post a new one. In a thread about Group B, forum member FAL posted this:

Quote:

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Originally Posted by FAL

GpB was never originally intended to be a rally catgory, only a racing category. The new Appendix J for 1982 (GpN and A) was introduced to ban the many, largely British Gp1/2/4 "homologation specials". Without an extension of Gp2 and Gp4 for 2 years and GpB, there would not have been enough entries on International rallies in 1982 and 1983.

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I'd be very interested in hearing more about this. What were these 'homologation specials', and why were they a matter of concern?