I used the CA legal cat from DEC... it works fine.
Here were the results with about 7 miles on the cat, stock '89 chip, no vacuum leaks, rebuilt injectors, new cap / rotor / plugs, new O2 sensor and perfectly dialed in idle and CO adjustment using a wideband O2 sensor. Literally rolled right off the highway and pulled in for testing.
About 10k miles later, this time with a different tune...and the car sat for about 2 hours before it was tested.
