'think' the 110 has an intercooler, otherwise similar if not identical (maybe diff turbo?)
This is comparing mk4 and Audi 90vs110. The 110 wasn't available in the mk3.
I assume the 90 can easily be remapped to 110+ without any other work. I ran a mk3 TDi 90 for a year and preferred it to the Mk3 Gti 8v I had before it.