You say it gets an 02 sensor code at times ? Well the 02 sensor can cause some bad drieability problems sometimes. When you floor the car the 02 is ignored and the car runs on programing from the other sensor readings (MAP , TPS , Coolant , RPM and others) as you said it runs good when floored and when the eng is cold the 02 is ignored at first until the eng hits about 120 I believe and the coolant sensor adds fuel like a choke which helps it run better cold. I would want to put a scanner on it and see what the 02 is reading when it runs bad. Ron