As usual there are many different thoughts and theories.
1) always check the basics. as stated clutch adj, shift bushings, trans and motor mounts etc.
2) as usual John Walker is spot on with measuring the assembled syncro and slider, unfortunately this can only be done when the trans is disassembled. We've returned a number of these parts that where out of spec. Many of these parts are no longer available from Porsche and must come from the aftermarket. In general this will effect only certain gears, those repaired. Typical repair is 1st and 2nd on a low milage car like yours.
3) This can also be a Clutch pilot bearing issue. If the trans input shaft isn't turning freely it will cause hard and or notchey shifting.
4) If it has synthetic trans oil in it GET RID OF IT. 901's and 915's don't like synthetic. We use ONLY Kendall 80-90 and if you have a limited slip Kendall LSA additive
5) Apples to Apples, are the other cars your driving equipped with the short shift kit? There is also an adjustment, pinch bolt on the shift tower that if over tightened makes it difficult to move left and right. Is the shift tower properly lubricated?
6) and last, are there aftermarket parts in the shift linkage. Many times we've seen "rebuilt" shift couplers with poly or bronze bushings that don't have sufficient play in them. O.E. couplers are not "tight" they have some play.
Marc Bixen
Red Line Service
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