Nope, great idea, it is much better than the original configuration. I did it to my B18B and restored the one on my D-jet car.

I was having some issues because my boosted brakes were T-ed off the PCV hose. There was constant rattle and I could not get the carbs to tune quite right. upgrading to the B20 fitting (which I also god from Volvo From Heck) was a great move that solved the problem.

Install it and you should be good to go.

Adjusting the carbs... that just takes practice. A trick suggested to me is to unhook the PCV hose and put a vacuum gauge on the intake fitting. Adjust the idle until the vacuum needle holds constant. This is supposed to show you (relatively) if your two carbs are sucking the same amount of air. The vacuum reading is less important than the vacuum needle holding steady. I believe this only works if you have a center vacuum port.

That'll help you with the idle balance, but the correct fuel mixture is trickier.
Just be sure you start from the same mixture point on both carbs (12 flats, 2 complete turns down/out) Adjust each carb three flats up or down. Use the lift-pin or a wide screwdriver to check the idle behavior.

Review those John Twist Videos. I was one of the first people to link them here and they explained a lot to me.