M5 Guru (>2000 posts)
Join Date: Aug 2007
Location: So Cal
Thanked 246 Times in 215 Posts
It looks like you do a lot of hard launches and your boost peaks above 9psi.
Iíve cracked my plastic one in the past as well.
As Shady mentioned, you need those 4 center mounting posts. Someone local tried what you did and the results were the same as yours.
You have few options,
Get an aluminum lid
Weld the bov adapter on the lower plenum, but you donít have to at 9psi
Get a CF plenum, if cracks have it replaced under warranty
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