there is a literal world of difference in the chips that are out there on the market. ebay chips are usually either copies of something else or home brew tunes that may be good or may be bad. there also seems to be an upper tier of chips/tunes also which are few and far between the normal bad, average and good chips out there. some of the best i have come across make other chips that people hail as being great and giving good gains feel nearly standard in comparison but like i said these are few and far between. the only brands i have seen in this sort of upper rung is Dinan and Autothority, both of which are incredibly expensive. also the Dinan chip is only tuned at full throttle so driving normally its the same as a standard chip, Autothority is similar at full throttle but also has very good part throttle maps.
forgetting about part throttle and just speaking in terms of power gained at full pelt the Dinan and Autothority chips trash Mark D, Jim Conforti/Turner Motorsport, Active Autowerke, Alpina C2/B3 and a host of lesser names/brands. have not seen anything more agressively tuned than those 2 bar some of my own creations which is, incidentally, why i shelled out on 9 zillion chips from here there and everywhere in the first place
@ speedtouch, i probably have some stuff u may be interested in. if ur curious drop me a PM. been quite a while since i was chatting with u previously.