14x6 4x108 were found on 4k(q), cgt, 80/90(q) etc. 100(q) also came with 4x108 bolt pattern, but their 15" rims weren't the ronal 16 spoke design.
15x6 5x112 were found on 5kt/5ktq/urq. (also 15x8 on the urq)
For a time back when those cars were current, you could get 15x6 4x108 directly from Ronal (they weren't an Audi offering to my knowledge). I think that's what you have or are looking for.