Where are you located? If you're making the intake manifold out of abs you should look into this
http://www.techshop.ws They have abs 3d rapid prototyping machine that can print out your design from a cad file. Membership is $30 a day, $100 a month, and $1200 a year. I'm not affiliated with them in any way I just think it's a great resource for a fabricator on a budget. I'm planning to use this for printing out a mold for a foam positive for lost foam casting aluminum for my adaptation of gixxer tbs. Got a question, can abs handle the heat cycles? Won't abs get too soft if it's heated up possibly deforming? If the answer is no then I may just forgo the mold and just print out the manifold.