There is a theory the HD TCVs makes no difference.
Many people (me included) experienced replacing HD TCV with no difference and replace the top 2 of the 3 hoses with silicon and got performance.
You might just try to replace the 2 hoses to silicon with the stock TCV and see what happensHere is a discussion
http://www.volvoxc.com/forums/showthread.php?t=20331
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