O2 Inversion Error!?

Hey guys, haven't been able to find any real solutions to my problem so I was hoping for some help.

I recently replaced both of the O2 sensors on my 93 MX6 LS because of trouble codes. It shut off my CEL for a bit, but then driving for about 15 minutes of freeway speed the light comes back on and gives me inversion errors for both sensors. Funny thing is that the CEL shuts off after decelerating. I put on cruise control the light comes on, I slow down and it shuts off! Kinda weird.

The car also takes much longer than it should to heat up to normal operating temperature. I was thinking that might have something to do with it but I'm not too sure. It really takes about 20-30 minutes of freeway driving for the car to get to operating temperature.

Thanks for any help, tags just expired so I really need to get it smogged!