I have read that a '71 -'74 Bug are fitted with D Jet FI.Can anyone verify and advise just how many parts are a definite swap? Or is it a similiar situation to a 411 motor and a 914 motor? The same but not the same???

Beetles got FI in '75.. at least on the east coast... and it was L-jet

L-jet and it's not the same as a 914 1.8

The T3 squareback, fastback, notch got the 1.7 d-jet system but different plenum, early ones have different MPS's

411/412 are a type 4 1.7 D-jet

late bay window buses got a L-jet, not quite the same as a 914 1.8

The T3 D-Jet is different from the 914 D-Jet in many ways. The plenum, the MPS, the TPS, the ECU. The systems were pretty much different from year to year in the T3, too. Early systems had no air intake temp sensor, but used oil temp instead. I doubt the T3 manifold parts will physically fit on T4 engines, either. Totally different heads.

I don't know anything about the 411/412 systems.