I would use the W124 603 non-afterglow relay. That will match the wires currently installed on your motor.

Then do the cheap and simply "afterglow" mod. There is a great write up on here, you simply wire in another relay . . says the guy who has the parts sitting on a shelf . . .

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87' 300DT (Grey w/ red leather)
87' 300TDT (silver w/ palamino tex) SOLD

2012 VW JSW TDI (on tdiclub.com all the time "btcost")