Originally Posted by ps2cho

It needs to be very, very hot. A few minutes won't cut it.

Like I said, freeway 70mph in 3rd gear. Hold it at ~5500 rpm for a good 15mins or so. Its the only way to heat the cat up enough to fly by emissions. A few minutes won't do anything. A new engine may be enough with all the computer adjustments, but with our older engines -- they WANT you to fail.