BMW e28 Turbo Question

Hi Bimmerfriend,

since I test-drove an BMW 524td of one of the gyus in the neighborhood some months
ago I was looking for one. Now I have bought a ´85 model from an elderly woman in
quite good condition. But what makes me wondering are the different performance characteristics of the two engines which presumably come from the different types of turbochargers. My bimmer has an small turbo with some external-looking wastegate:

<IMG src="http://img46.imageshack.us/img46/6482/ssa50187nx3.jpg" alt="http://img46.imageshack.us/img46/6482/ssa50187nx3.jpg[/link]

<IMG src="http://img175.imageshack.us/img175/679/ssa50188hf2.jpg" alt="http://img175.imageshack.us/img175/679/ssa50188hf2.jpg[/link]

The one of my neighbor is much bigger but with an standard wastegate:

<IMG src="http://img46.imageshack.us/img46/6393/ssa50189cq8.jpg" alt="http://img46.imageshack.us/img46/6393/ssa50189cq8.jpg[/link]

My diesel develops torque at already 1500rpm while the other puts out sufficient power not until 2500rpm. Anyway, my engine has an much quicker throttle-response.
So how about this differences? They are both 85-models. Had BMW switched to the other chargers during time of production? I have seen an engine of an 91 model 524td e34, too. It has an EGR but no external wastegate.

Regards, Jim