I'm reading your description of the problem and it's ringing very true to what I'm currently experiencing with my Subaru Legacy, certainly the metallic whine and on the odd occaision a lack of upchange. Time for a manual conversion i think as mine was rebuilt 15k miles ago, guess the auto box struggles with additional power.
Regarding your car, I may have a cheaper solution if you want to keep the car, drop me an email and we can talk.
Ryangordon86@hotmail.co.uk