I was just thinking yesterday that there must be something wrong with the flaps in my heater box - because although the air comes out of footwells fine (when selected), face vents fine (when selected), on the demister setting the air doesn't come out at footwell or face vents (good) but makes a whistling/hissing noise and doesn't seem to come out at windscreen level either. It seems like an adjustment issue to me, like the flap is not quite open to the demister vents at the end of its travel, but the only way to really find out will be to take it all apart, which looks like being a complete dashboard strip (usually not for the faint hearted).
It will be easier if the dashboard comes out as a complete sub-assembly (as it does on the 164) - eLearn, unfortunately, seems to have no information on this.
Squeaks from the suspension are, I believe, usually from the upper wishbones, above and behind the front wheels. Try spraying some silicone spray at the bushes for a temporary fix (to confirm the source of the squeak), then disassemble and grease with rubber grease or replace as applicable?
Knocks from the suspension, on the other hand, seem to usually be anti-roll-bar related.
Petrol gauge light - you mean the night-time illumination or the low-fuel light? Neither is really all that bad - unlike mine, at least your fuel gauge works?
See the recent thread on this (http://www.alfaowner.com/Forum/alfa-...emp-bulbs.html
) and go to the linked thread that shows procedure for a pre-2002 model. About a half-hour job.
As for the wipers, sounds like brushes in the motor to me (I think high-speed has a separate brush).