TDI 90 and 110 engines are distribution pump diesels, and have the pump driven by the cambelt. It's a big block on the offside of the engine bay with fuel pipes going to it and four hard metal pipes going to the injectors. You can only really see it with the engine cover off, though.
My old TDI 110 looked like this with the engine cover off:
The only difference between the 90 and 110 engines is the turbo, which is difficult to see. Best to check the build
sticker, but bear in mind that it only tells you what engine the car came out of the factory with.
My current build
sticker (with the chassis number blanked out of course)
The engine power in kW is shown as part of the code on the
sticker - mines 110 kW = 150 BHp.
96kW=130BHp, 81kW=110BHp and 66kW=90BHp
TDI 130 and 150 are PD engines, the injectors are under the cam cover and fuel pipes go from the fuel filter to the flywheel end of the engine where there is a low-pressure pump to circulate the fuel to the injectors. Again, only easy to see if the cover is off.
My TDI 150 looks like this under the cover
TDI 130 has a side-mounted intercooler so there should be no boost pipes going across the engine. TDI 150 has a front-mounted intercooler and the boost pipe from intercooler to engine inlet goes across the front of the engine, behind the oil filter.