l recently acquired a 93 Jetta GL IIl in a trade, sohc 2.0, 5 sp. Not really into the whole import/tuner thing anymore (and am not a ricer l know wtf i'm doing) although i've had some very nice tuner cars. Anyway, l do not plan on putting too much into this car, i'm just the type that i've got to mess with it a little it is just my nature. What, realistically, kind of gains should l expect from...
light cam gear, lightweight pulleys (underdrive pulleys, etc.), light flywheel, maybe a header and intake, in terms of power gains, acceleration and whatnot.

Hop up mods for VW is pricey & really not that many of them. More chrome than anything else. l would not bother. It is the domestic car market the accessories makers have their eye on so make more crap for them.
Really, if u know what u r doing then u know that the manufacturers put the best for the buck that they can on their motors already - so the rest is just hype.
You forget that Ford is in competition against Chev & Dodge..and if a light flywheel really make a difference do not u think they would have done it? But they don't. Nor headers or other. And the car makers have the testing faucilities & the bucks to spend on ''R&D''.
It is a buck grab by the accessories manufacturers.