03 California Honda Civic hybrid W/ 170K miles --

The long story short.... Noticed hesitation during acceleration. After some troubleshooting noticed I had a bad coil pack so I replaced all of them. Car seemed to run great. 3 months later check engine light comes on for misfires again. Checked coils, again had multiple bad (or so I think). Also p0420 came on indicating bad CAT. Changed spark plugs and coils. Bored out my CAT and tried defouler trick in attempt to spend absorbent amount of money. Heres the problems....

This car has 3 02 Sensors. Most advice I have read says that the primary is the only one responsible for A/F mix and therefor the most important. #2 and #3 just report back on if the CATs are working. HOWEVER once I installed the defouler, I noticed significant difference. Large loss of power and around 4k RPM it would almost sound like it was hitting a "REV limiter", however oddly enough, no check engine light. Took it to a dealer who could not difinitivly determine the problem, they just recommended (starting with a new CAT)....

I removed the defouler and put o2 back in. This changed symptoms slightly, not as much hesitation at high RPM, however getting to 60mph under load is very difficult (large loss of power)... As expected the code pops back up now (po420).

Apparently the #2 o2 sensor must have some effect on A/F mix because of the above tests. Can anyone give better info here? Are the CA version different? The CAT is gutted, so why are the downstream o2 effecting performance?

I read a post tonight from a user saying he "defouled" o2 sensor #3, and that did the trick....

Im trying to avoid buying a new CAT, and cant understand the actual importance of 02 sensors #2 and #3 on the A/f mix and timing in general....

PLEASE HELP!! Thanks in advance....