Back Pressure

[Reu Froman]

How much effect does the cat have with back pressure. I have a home modified "high flow" cat currently. Will that jack anything up with my engine?

[WeST]

Depending on what you did to modify your cat it shouldnt have much if any effect on your engine and I would doubt you would lose enough backpressure notice any loss. Straight pipes only yeild about a 1-6whp on NA cars. Only way you would notice a loss would be if you ran a Turbo exhaust on a NA car with a gutted or modified cat.

[Mark_H]

Yeah it depends on what you modified etc, so we cannot answer your question without knowing what you did to the cat.
Mark

[gothemperf]

Unless you did something to increase the back pressure you shouldn't notice any loss, in fact its more than likely that you are doing nothing more than emitting more pollutants.