Paint a test piece first and see if the sealer chemically melts the PLA? ABS?
I still think you are on the right track 3D printing a prototype like that. I get that the temps will be hard on it. Still, you should be able to make some great data collecting short runs with it. You could always set up with tools so you could quickly pull the manifold off the motor between runs.
I can't wait to here what you think Tom!
