My AMAL valve is long gone, although the nerds on here will know how to make it work better

Could change to an external wastegate. That usually makes boost more stable, but pricey.

I do have an external wastegate, and I'm using a manual controller that works on the principle of an external wastegate, in that it has an adjustable spring pressure that only allows the wastegate to see boost, and therefore open, once the desired level of boost has been reached.

The main advantage is it's SO easy to install, adjust, and it's SO CHEAP!

In fact, you could likely install this on the airline to your turbo wastegate, keep using your AMAL valve, and still see an improvemnt in turbo response and steadier boost up top.

Here's a link: http://cgi.ebay.com/ebaymotors/NXS-M...Q5fAccessories

There seem to be lots of companies selling them, some are UK based too

Make sure you get this set up on a dyno or have your air/fuel checked, or the money you save buying it could be spent on your melted engine