I installed a 76mm pulley and raceiq tune on my 07 sl55. The stock pulley had a .35 gap with one shim and was very smooth. I installed the VRP 76mm with no shims and its at 1mm. Actually was 1.1mm when I first installed it. The car now has a choppy acceleration over 1/3 throttle and bucks once when letting off of heavy throttle. Tuner says the gap is way too much and VRP says the pulley has to wear in? I didn't have this problem on my 03. Thoughts?

It wont "wear in" they want you to use it so they won't have to refund you for a defective pulley.

clutch disk is worn and a new pulley doesn’t usually account for it. my UPD 83 is at like .68 or something like that

I have the exact same VRP pulley with a .63 (25 thou) gap and the SC engagement can be noticeable depending on throttle position/revs.
76mm is quite aggressive and will give occasional heavy engagement IMO.
Not sure about the bucking when letting off throttle being related to the SC pulley and it's gap?

Agreed, 76mm will be harsher regardless. I actually pressed the bearings and metal spacer out of my new pulley, machined the metal spacer down a little, and reinstalled so the pulley sits deeper and the gap is closer to spec. Biggest concern w/ a large gap is wear and failure of the springs on the pulley.

Bucking I would point towards tune rather than gap. Pulley should stay engaged until stopping, same as stock, so gap would not be relevant. You could drive w/ STAR and watch for when it engages too to see if it's doing something it shouldn't.