installing intake
Yes, the yellow thingy's stay in there. No problems. Are they worth it? Yep. There just holding the gasket in place while you do what you have to do. Think of them as a third hand helping out that you can forget about.
The grey end seals can be used. But do not trouble yourself to much if they do not fit or stay to well. There a stock item and will only save the use of a ton of RTV.