[350HP930]

If you have passed your test leave the test pipe on till its test time again.

I have no idea what back pressures are normal before a cat but I know its more than no cat and turbos love low pressure after the turbine.

The turbo will also increase back pressure to an amount close to the level of boost so my above pressure calculation would be in addition to those 'normal' restrictions.

If you are really curious you could tap a hose into the exhaust (there is an access port near the O2 sensor) and get some pressure readings.

Being in a non emission testing state I could never imagine paying good money for a catalyst and if I lived in california I would certainly try to cheat the system any way I could.