[quote=intergrated j 78]..... The previous owner had decided to sawzall the catalytic converter off and replace it with a turbo muffler, so the lack of exhaust back pressure makes it impossible to fully tune it.....
Just a general comment on this concept of "lack of exhaust back pressure" causing a problem. This statement is not uncommon on the internet, though not technically correct. Lower pressure at the exhaust port when the exhaust valve is opening and closing is desirable, with some qualifications. Exhaust pressure is affect by 1) quantity of flow, 2) pressure pulses communicating from other exhaust ports (a good example is on oem cast iron exhaust manifolds), and 3) pressure pulses reflected back from the end of transitions (exhaust runner terminations at collectors or mufflers or catalytic converters). Removing the catalytic converter may have negatively impacted the tuning of the exhaust system, probably altering the timing of the positive and negative pressure pulses at the exhaust ports, but not because it reduced general back pressure.
