If I were to look at buying a classic Impreza would it be obvious if the maff sensor has gone?

Would the car still drive the same. I don't really think me faffing around under the dash with wiring is what the seller would want to see.

 

Yes it would be obvious, warmed idle would be erratic and would stall at junctions etc. Whats harder to diagnose is a failing Maf. If you buy a 99/00 then I would change the Maf as a precaution, these are notoriously weak. They cost around £90 and are easy to fit. The Maf is important so changing it would give you peace of mind. If its got an induction kit fitted seriously consider removing it and replace with the original air box.