Hello
Wish I could answer....I scored a set for my ST4S (996 motor) 'cause TPO stated that they would fit, but the handsome velocity stacks were a good 3/4" too tall to fit under my DP air filter.
TPO was very responsive in taking them back and refunding my $$$, although they still list them as fitting the ST4 on their eBay site.
All of the feedback I was able to find on 'em (mostly from Monster folks) was pretty positive. Noisy, but effective. I think the Monster setup uses individual K&N filter pods.