O.k., so no one was interested in my last post on the whistle I got in my '89 740 Turbo, with Mitsubishi water cooled unit, after changing the exhaust manifold gaskets. I'll try another approach, pose a possible cause, and see where that leads. Here's a theory: I somehow damaged the wastegate actuator while reinstalling the manifold, for instance by snagging the actuator rod, and now the wastegate is not opening per design. Could this cause a whistling noise? Also, this car has more power, and runs hotter, than before the job. Sound like too much boost? Is that what happens when the wastegate actuator diaphragm gets broken?

Thank you in advance for any and all advice.