Sort by Manufacturer... SLOW!

Loading the manufacturers list isn't a problem, however, when you select one of the manufacturers, it is REALLY SLOW!

After selecting an option the page load time is:
Parse Time: 11.788 - Number of Queries: 38241 - Query Time: 3.12004679495

For comparison, front page load time, with 12 latest products and 8 best sellers shown:
Parse Time: 0.665 - Number of Queries: 505 - Query Time: 0.237525555328

Contact us page, i.e. a page without the latest products and best sellers:
Parse Time: 0.302 - Number of Queries: 74 - Query Time: 0.0141262902679

Is there anyway to make the load time quicker for the select by manufacturer?

7239 Products
2391 Categories

Would adjusting the SQL_CACHE_METHOD help?

Currently I'm using

define('SQL_CACHE_METHOD', 'database');

Here is a weird one, which will make sense to the coders out there, I guess it is due to the way the two methods search the database.

If I search for "Acoustic Solutions" I get this result:
Parse Time: 1.387 - Number of Queries: 2092 - Query Time: 0.685017476654

If i select "Acoustic Solutions" from the drop down list it get this result:
Parse Time: 12.589 - Number of Queries: 40035 - Query Time: 3.43918967332

What i've done for now, is create a search term for each of the 85 manufacturers instead of using the manufacturer drop down, that way the customer isn't kept waiting.

Without actually seeing your site, the explanations you are giving are not providing enough information to determine the reasons for the speed issues ...

At a guess, the Manufacturers dropdown may have the Category Drop down on it ... how many Categories are in that list? If it is huge, then it has to output that dropdown list ... if that is 100-3000 Categories that is 100-3000 lines to download and depending how many are there it will take a week ... or 11 seconds ...

A search for a manufactuer's name doesn't have the Category dropdown, that is 100-3000 less lines of code on the screen to download and will be much faster ... or 1.3 seconds ...

The menu loads instantly, the problem is, if you use the manufacturers list and select from one of the 85 manufacturers it take ages to load your selection, if you just search for the manufacturer using the search box, it loads far far quicker.

For example if I select "sony" from the manufacturer's list it takes ages to load
but if i just search for "sony" it loads far far far quicker.