I've wrapped downpipes, but I mean it's the same thing. Metal pipe. Manifolds are just more of a PITA. I liked Sleepy_Steves method of using RTV to hold the ends in place/prevent unwrapping. It's ugly, but under spray, who will notice.
Now, the silicon spray does help, yes. It's another barrier, but it also protects and prolong the life of the wrap. The downside- your wrap you wet to install has to be dry, and pulling a mani back off is a pain in the ass. Solution? Same as with the downpipe. Set it down after your wrap is wet and secure, i.e. done. Insert a heat gun in one end, and watch it cook. All that nasty cooking smell is gone before it hits the car, your wrap is cured, and you can go ahead and spray.
For the few bucks it costs, get the spray. If nothing else, it'll give the mani a nice coat. If looks worry you after, can always use the 2k+ degree paint (think its 2k, its something stupidly high, vs the engine paint that's 700.)
Boostin likes Feria, Feria likes Boostin, I like Scoot, Scoot likes hatch, hatch likes feria, everyone likes Boostin, nobody likes me
And college kid is jealous he is not involved.