Hi Lennyhope,
Yes, the 1.4 TDI exists with two different power outputs: 75bhp and 90bhp. Contrary to what Leopard says above, both were available in Sport guise, but this has nothing to do with the engine; it's a trim level, determining which options were fitted as standard.
The TDI90 is much less common as it was only available for a short period and was sold alongside the TDI75. Consequently, prices for the 90 tend to be fractionally higher.
Although some members with a 90 have posted very high fuel efficiency scores, the general consensus is that the 75 is marginally better on fuel. Furthermore, the 90 is widely acknowledged to be less reliable than the 75, principally due to its fragile dual mass flywheel and (to a lesser extent) its variable vane turbo.
In short, if you're looking out-n-out frugal motoring, the TDI75 is probably the better option for you.
All models were available in three trim levels -
Base is the basic car: no bells and whistles, but also as light as possible.
SE adds some nice comforts such as climate control and leather steering wheel, etc. The SE is the most common trim level and can be recognised by the classic 6-spoke alloys and the addition of front fog lights.
Sport models can be recognised by their 17" 9-spoke alloys. The major advantage of a Sport from your perspective is that DIS (the in-built computer than tracks average fuel consumption) was fitted as standard. With Base and SE models, this feature was not included. The drawback of a Sport (unless you swap them) is that those 17" alloys are bad for fuel efficiency.
All toys were available as paid-for options on all trim levels, but finding an SE where the original purchaser chose to add DIS is a challenge.
I hope this helps. Your questions have been asked and answered many times before, so a search is likely to lead to the info you seek. However, the forum's own search feature is rubbish, so I suggest using Google and including the term site:a2oc.net at the end of your search term to limit Google to the contents of these pages. Anything you can't find, just ask.
All the best with your hunt,
Tom