Thomas Pindelski, a contributor to this forum, has a detailed write-up on intake manifold overhaul on his subscription-only website, pindelski.com. I would not have been able to undertake this task on my 500 SEC without his site, though as it turned out I went even further than he did in the pictorial. (Perhaps the most glaring omission is a discussion of the correct mounting of the throttle position switch. You do not want to get this wrong given the difficulty in getting back at it later.) His subscription fee is ridiculously modest and will pay for itself many times over just on this one job.