DDK - Die Deutschen Klassiker

After posting above i checked the internet and the PET catalogue where there is no mention of shims, However on some forums there is mention on later cars of self adheasive shims. This might be the material i have on the pads whicj is showing signs of indentation.

The pads obviously have anti squeal pads on them, so no shim should be necessary. However as has been mentioned it might be worthwhile making sure the pistons are correctly orientated with the relief being in the right quarter. It might also be worth getting another set of pads, just a decent std pads like a Ferodo and see if that makes a difference.

But you’ve probably done that already

My ref to shims..
I have A type front callipers and they have the L shaped stainless shims and are sandwiched by the piston and the back of the pad.
The must fit the recess machined in the piston or the pad is not supported on braking.
ATE would only do this complexity for a good reason.
My brakes squeal, but due to the high performance pad material I use.

Not sure if the op has M or A callipers.

Refernce above, I have now checked the internet and the PET catalogue but there is no mention of shims. However i found reference to soft shims that stick to the back of the pad. This is what i might have on mine which is being indented by the piston.

The brakes do not squeal. if i brake the noise disappears and brakes work normally. Does not matter if i brake softly or press hard there is no squeal. when brake is released the droaning comes back after a short while and it is constant. I have a classic mini on the ramps at the moment which i have just restored. its comming off this week and i will be putting the 911 on and stripping again to chck all the above suggestions

After all your suggestions and attemps i made to solve the problem i gave up and took it to my local garage genius. It is embarrasing to report that he took one look at the "NEW" pads i had fitted some time ago and sais dump them. Fitted new pads and problem has diappeared. Cannot remember where the pads came from but made sure this time i specified a well respected manufacturer and its solved the problem.
Car is now sold and being picked up tomorrow. Sad to see it go after 19 years but i still have my 356 and have decided the time has come to stop working on them and to start using them regularly. Roll on the summer.
Thanks again for all your suggestions

Never come across that before, learn something every day.