If it has the factory exhaust it should be a 4 to 2 to 1 tri Y header and down tube. The GTI exhaust is a bit bigger for the 1.8 engine and gives more flow. THe PCV tube coming down on top of the air filter is great for fouling it. You may want to add a washer inside the pcv or crank case breather hose thats right on the top rear of the valve cover to keep the oil in the engine.
Yes, get a free-er flowing filter. Dont recall if the diesels like that like hot or cold air. They made a super charger for those that is driven by the cam sprocket,but its hard to find.
Yeah, my father was a fan of the type 17. His was crushed by a tree in one of the hurricanes that came up the east coast.Maybe Gastone?
The dasher has a 1.3 engine or 90 cid, so that is a bit larger.