can't autoscan with 409.1, just choose the engine blocks you want to log.
there is a link somewhere on here or google which blocks are MAF related.
you can also choose to display engine related fault codes which will show up an specifics.
what is the engine like at part throttle, especially coming on and off the power?
knock a lower intercooler pipe off an see how much castrol there is in there.
a damn good clean out with some thinners can lower intake temps considerably if you are pumping hot air through oil soaked pipes and I/C. its an old car and any seal problems will give you a crappy intake.
that coupled with a knackered MAF will see your ECU pulling your timing back and a lack of power.
pull the MAF plug when idling and see what happens. then try revving with it on and off.
if no difference take it for a short (gentle) drive without the MAF plugged in. if any of those demonstrate smoother driving, better throttle response, better idle then it is Defo screwed.
but a VAGCom is the only way to see what it is reading
I've had 1999(V) 1.8t quattro sport, engine code AJL, for 3 years now and over time have noticed a drop in power. It has been regularly serviced, new plugs and stuff. It is pretty standard apart from a Pipercross panel filter. I have noticed some oil in the vacuum pipe leading to the inlet manifold and air intake. Something I have noticed is the kick when the turbo kicks in is hardly noticable anymore but you can still hear the turbo sucking air in. Any pointers or advice would be great as I'm getting annoyed at being overtaken by ****** Vauxhalls 
