Did you use a OEM front O2 sensor. If not, do that next time. Trust me again. the rear O2 can be after market...so far mine is good, but I had to replace the 2 year front with a OEM one last month.
Same with Hubs, front should be OEM, rears can be Moog
198k, 5/20/12 new ej257 short block, 8/20/11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.
Engine Build - Click Here