Fabspeed Bypass Pipe-Any Experiences Welcomed.

[jaykay]

Does current information suggest that installing secondary cat delete pipes and a Pedro style/pse style bypass exhaust muffler (modified stock s) will reduce back pressure (and therefore alter exhaust scavenging) to such a degree that there are losses in torque and power? Can one simply look at what the computer has done to ignition timing to see if it has detuned the engine via ignition retardation, to get an idea whether an exhaust system is working well? What are the stock ignition parameters and what variance would be bad as seen via the OBD port?

Yes I know dynos are the tool I am dancing around!