The K-731 retrofitting Kit, from Redline-Weber, came with two different sets of four bolts, to be used to bolt the first adaptor plate, to the intake manifold; one set at 6 mm the other set at 8 mm; however, only the thin ones fitted on the intake manifold without modifying it, but their heads were tiny and not enough to fill the openings for them at the adaptor plate, which felt loose; the thicker set of bolts would fitted perfectly filling the openings on said first adaptor plate, but to use them required a drill and tap job on the intake. Here's are a comparison photo of said two bolts:
So, at first I used the 6 mm bolts on the Intake Manifold, which ended being loose and with time, it developed a huge vacuum leak between said first plate and the intake manifold, which was more noticeably when the engine was working at normal operating temperatures.
So, I sent the intake manifold to a mechanic Shop where they helped me to drill and tap the threads on it, from 6 mm (~ 1/4") to 8 mm (~ 5/16") in order to solve this issue.
I asked them to do that, because I was afraid to drill further deeply than specs, reaching the Coolant crossover passage that is Underneath, that would've Ruined the intake for sure. But they do that job perfectly, and the 8 mm bolts solved the loose plate problem, and the vacuum leak for sure.
Edited by Loyale 2.7 Turbo, 01 October 2016 - 10:00 PM.