I'll add a few comments on my experience with this adjustment. Yes, you do need a nut on the upstop bolt - I didn't know that at the time, and didn't have a metric nut to fit. Since I had cut out the rubber upstop, I left the bolt in place, with an english nut just on the end to keep the bolt from completely coming out until I could get an M5 nut the next morning (big mistake) Test drove the car and it was much much better for H&T. The next day, on the way to work, at one point I floored the car to test WOT - well second big mistake
. The throttle stuck OPEN - I notice when I went to up**** and the rev limiter kicked in. Luckly, I was in the left lane - I let the clutch back out to get the revs back down and turned the key off to kill the engine, coasting to a stop on the side of the road. When I examined the pedal, all appeared fine. The throttle quadrant was stuck open part way, so I pulled it back to idle. Checked the upstop bolt, check the throttle adjustment point to see if it was loose. Cautiously restarted the engine and it appeared to be fine. Good for me, as I had no tools with me!
All I can think of was that either the upstop bolt got caught sort of sideways (since it was not tight with the english nut), which would cause the throttle to be stuck partially open, OR the cable was pulled too tight and got bound up on something.
I readjusted the whole thing again - the black metal bracket which holds the upstop bolt was bent slightly (causing the pedal to come even further forward, leaving more slack in the cable), so I bent it back - has anyone else seen this?
I readjusted the downstop to prevent as much pedal travel, and also readjusted the throttle cable near the quadrant. I think it is right now, but I'm going to have my dealer double check it to ensure I'm not stretching the cable.
I can now H&T the car much much better, so this is well worth it, but just be careful with the adjustment - I should have been moreso than I was....