Just another little update. Still trying to play with loading at temps for FEA but I'm also trying to find a similar material to CF Nylon instead of ABS. Loading numbers without a specified elevated temp show the unit is quite strong, with a FOS of around 20 with 50 lb loading (I just weighed the throttle setup and it's 5 lbs for reference). Displacement is also .04mm or less at any given point. Still not as credible without the temp being added but shockingly solid results (although my walls are .25" thick lol). I looked around and for even more piece of mind i found a spot to add a simple brace starting from the valve cover to the throttle bodies, relying on some tension to keep it still and strong. More to investigate but so far this is what I've done.

Also, is there a way to change the thread name? Most of it has been related to things other than its original title. Not bad just misleading lol.

Not sure if I had answered you on the 45mm vs 42mm setup question, but I have some data now. The 42mm setup definitely makes more low end (from my virtual dyno pulls 3-5 ftlbs) about everywhere. The higher port velocity definitely helps. I would have stayed with it but due to the fact that I have to deal with the oval downsize after the throttle bore for the Yamaha throttles, I decided to go up. I just put the R1 throttles on this weekend, and after tuning them, I can't say I feel a loss in torque really, although virtual dyno says otherwise. The 45mm make more power up top, so maybe that's where it balances out. The thing I also like about the 45mm is the headroom you have to continue with bigger and better mods like cams, compression, exhaust, porting, etc. Currently, I have a stock exhaust for the most part, and have definitely been missing out on power and torque as a result. I'm going to nab a RB header and race pipe and that should make the setup pretty healthy. Car sits around mid 120whp from virtual dyno's numbers currently, but I am looking forward to seeing what the exhaust can do. I'm probably going to check back pressure soon so I can post it here if I get to it to verify or deny my suspicion. I am also planning to take it to a real dyno once exhaust is on and things slow down to see how good of a sim virtual dyno is.

For your setup and design I would go with the 42mm throttles.

Oh and small update on checking the manifolds strength. Was able to get a material data sheet. Heat Deflection Temp @ 264 psi is 289*F. I will do some math later to check the stresses but as far as the temp goes I can wrap my hand on one of the runners while the engine is running and hot and I can leave it there for at least 10 seconds. Looked at some average pain thresholds and anything hotter than 120*F at the hands is something most people can't sustain long at all. This goes in line with say a hot cup of coffee.

I am reviving this 2-yo thread to give you some additional information about how our project endend, as you had seen the 3d first study. It requested two additional year, mostly because our company had changed a lot during the project.
At today the car runs on 3d-printed nylon intake manifold, printed using SLS-powder tech, as the FDM cannot guarantee the vacuum needed.
The ITB (42mm) has 4 runner mounted on it (FDM) wich are encased in a plenum wich function also as a filter housing a-là m3 e46. From below the plenum, a direct duct take the air from driver side bumper intake, which had made necessary to "mirror" the alternator on the hot side.

The car -as requester by customer- has a very OEM finishing look into the engine bay, a very hard low grunt albeit it has remained N/A and original dispacement.
Final figures: 162 hp @ 6600 rpm, 195Nm @ 4500 rpm.
The car drives well and customer is happy, also because the car was tailormade up to him requests and well into one of those "prototypal adventures" which are very uncommon here (in italy a lot of customer prefer adhere to tried and tested ways).

https://cimg5.ibsrv.net/gimg/www.mia...10590ec12.jpeg
https://cimg6.ibsrv.net/gimg/www.mia...26ded1d5b.jpeg