Back when I was racing my 914-6 I had one of the first RennShift units and in talking with the maker of them I learned some things, not in any particular order. Make sure the trans mission is in great condition for the bearings and synchros. Make sure the firewall bushing is new or like new and I finally bought one of Jim Patrick's replacement bearings. Make sure the coupler flex joint is like new and I bought a sealed aircraft type used on many race cars from a guy in Maryland, sure was expensive like $150 or so. Make sure the bushing in the transmission shift console has little to no slop in it as the same with cup bushing. Since the shift rod wears from an oil and dirt mixture even a new bushing may not help. There are replacement bronze bushings but I went with a new neoprene one and looped several small nylon wire ties through the hole and around the console to tighten things up a bit, cheaper too.
When I installed the new shifter I had the rear of the car jacked up and moved the trans mission into 1st gear. I had written the shift pattern on the trans case as it is NOT the same directions as the shifter. I had both front and rear rods in place, inserted the shifter and got the pinch coupler in place without moving the rods. I had my daughter (who is a PCA Parade autocross champion) underneath the rear holding the vise grips I had clamped on the rear rod to keep things from moving. I tightened the pinch bolt and adjusted the shifter throw as per James' instructions. I forgot to tell her to let go and take off the vise grips and I could not initially move the shifter and it scared the hell out of me! Once we did that and set the adjustable stops the trans shifted great. I drove around some to get used to things as the feeling of the shifts is definitely different than stock. I found that in the street circuit races I did in Mexico I could actually shift into 1st at 30 MPH which helped on a course that had slow, tight 180 degree turns!
Hope all of this helps and the biggest thing is to make sure the trans is in 1st to get the shifter in correctly. Good luck. Here is the coupler I mentioned.
