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The wind screen is about is a touch off from closing all the way, the top glass has about an 1/8 inch gap between it and the rear glass. Are there any adjustments to the top I can make before I tear into the drive motors, also what is the acceptable gap in the seal between the top and rear glass?
The position of the glass roof panel is easily adjustable, and its surface should be flush with that of the rear window. From inside the car, loosen the axle bolts (that's what Porsche calls them), push up on the roof, then tighten them while pushing up on roof glass. There are two axle bolts in the front (each with one allen screw) and two in the back (each with 2 allen screws). The fronts are easy. The rears are a little harder to see. Just move shade until you can get a long allen socket on the screws. Porsche even put out a TSB instructing dealers to check the tightness of these little screws since they can loosen up over time causing the roof glass to sag. It's a 5 minute procedure once you've done it.
I wouldn't worry about the gap with the seal in your picture. Just make sure the surface of the roof panel is even with the rear glass once closed. The Targa is not unlike a sunroof from other cars of the era. It's not designed to perfectly seal; instead, it channels water to drains in a controlled fashion. Once adjusted properly you should have no wind noise and no water ingress in the cabin.
The height of the wind deflector is even easier to adjust. There is a nut on each side that you can easily see once it's open. Just loosen those and adjust as needed. The wind deflector is not supposed to be flush with the roof. It should be ~1/8" proud of the roof glass when closed, otherwise you'll get some noise. This is also described in a TSB if memory serves me correct.