3.0 cross over pipe and headers...

I am currently running Bursch headers on my 3.0 914 conversion with twin turbo mufflers. The pipes take a 90 degree turn off the headers, cross each other and lie in tandem where the stock muffler used to be. The exit pipes on each side have a Power Tone tip...sounds really nice and it really improved my bottom end acceleration...

My question is, has anyone running a 3.0 with CIS, ever run this kind of setup and THEN put in a cross over pipe? I have heard that this motor appreciates the scavenging effect of the cross over. Beyond a back fire when I hit the rev limiter, I have no other problems....

TIA