After a year now iam getting SES codes po 420/430. I have long tube heaers no cats, and have turned off all o2 sensor with the Diablo. Could a small exhaust leak cause this problem. The PCM was tuned when it had an exhaust leak last year.(not knowing there was a leak). I fixed the exhaust leak this weekend, but it still throws these codes, after a test drive a random missfire code came up as well. Cleared it, and it never came back. But still po420/430. Has anybody had this problem before?