Does anyone know how gutted pre-cats compare to a straight pipe in their place? I've heard of a 'turbulence issue', but I'm not really sure what this means.
Is there a significant difference for power?
Is there a significant difference for noise?

 

The exhaust gases have a bigger volume to occupy in the gutted precats/cats. This larger volume allows the exhuast to cool down thus slow its speed out of the system. A straight pipe will be better overall.
As for noise, have you gutted your main cat also? If not , the noise shouldnt increase much by gutting just the precats. I have gutted my precats, kept the main on and exit out of corksport single, I dont think its that loud.