Yes that is a confused set up, Vitesse MAF as far as I know needed the Vitesse chipboard in the ECU. Any Wideband sensor and associated gauge will tell you what the mixture is like (Will need a bung welding in the exhaust - usually done just as the exhaust pipe is about to head under the cabin floor on a 944) you will then be able to play with the ecu switches links according to the chips / board in the ECU to see how close you can get with what you have.
You can also get a piggyback e.g.
http://www.vitesseracing.com/html/piggyback.html to massage the fuel and ignition - I think it is actually a
https://www.perfectpower.com/index.php/products/piggy-back unit form here and they are bit more from vitesse but you get the wiring diagrams and base settings for a 944 if you go the vitesse route. This needs some skill to set up and is just an extra box outside your existing ecu. Your ECU may have many years of happy operation left but it is already 30 years old so it may not!
An Augment or VEMS is a custom new ecu for the 944 as that should have more years in it than the original but they were designed on smaller budgets than the bosch original.
The ultimate solution maybe to go with a Motec / Link or similar standalone system - that requires a lot more work and ideally you want someone who is an expert on the chosen system and on the 944 - you will also need to spend some time on the Dyno to optimise the setup. ( I think that there are some tricks to getting the best out of a 944 engine - thats how off the shelf chips were able to produce more power than custom chips by Wayne back in the day - I don't doubt Wayne now know those tricks as it would have been in his interest to decode them!
The cheapest option will be to throw in a wideband ands see where you are on the current set up with its dip switch options - then if needed go and see Wayne.
I believe all the chip / boost options come with an upgraded (3bar) fuel pressure regulator - you didn't mention that - and most have the option of bigger injectors.
You also want to make sure (pre Wayne) you haven't got any boost leaks (pay particular attention to Idle stabiliser valve / throttle body / small vacuum lines / intercooler couplings and you will probably want to do something with the wastegate and boost control system.
Whereabouts are you located?
Best Regards,
Tony