The fun I've had with the Throttle Valve adjustment on the 700R4 on some prior builds is part of the reason I've decided to go a different path for the transmission on my swap.
Even if you're using a TV kit, such as the ones at
www.bowtieoverdrives.com, it can be a bear to get it right. If you're "rolling your own" on the TV connection to the throttle.. Then things can get REAL fun. In "stock" installs, such as my 90 C2500, the throttle arm rotates about 90°, and the "pull" on the TV cable is fairly linear, with the angle established between the throttle shaft, TV cable attachment point, and the TV cable hitting 90° at about the half-way point in the pull. (Actually a bit before that, but not by too much..)
If the angles of a custom install don't match these, then things can get real ugly trying to get all the points to line up, and you likely will wind up with some VERY non-linear operation even if you get idle and WOT licked. And, if the total rotation of the throttle shaft / levers is something other than about 90°, it's going to be just about impossible to get it right w/o some custom linkages. I've not looked at the total throw / angles of the VE throttle levers that much with TV in mind, but I know when I was first thinking 700R4 something in my mind went "that's not gonna be easy.."
One thing I can say is this: You WILL need a pressure gauge to have a hope of getting it correct for all modes.
The other thing that can be a battle is the governor. If you just put in the "diesel" governor, it's not going to be correct for our application. I noted you indicated that you had the shop put heavier weights on it, but what's the thing actually set for? And, you'll need a different setting depending on what your actual attainable RPM is out of the engine.
A very good writeup on TV and getting it right is here:
http://www.tvmadeez.com/article/index.php