here's the deal...my car feels sluggish when its cold. when the car shifts from 1-2, and from 2-3, it kinds stumbles. but when it warms up, it runs fine. it runs fine under WOT. i have replaced my front 02 sensors twice. the first time with bosch, then the second time with ac delco's. P0133 keeps coming back (Bank 1 Sensor 1 slow response). Both times after i replaced the 02's, the car ran great. It was prolly 3 months after i put the delco's in when i got P0133 AGAIN! What the hell is going on? This is starting to **** me off.

one theory...i've heard that reduced back-pressure can cause bad o2..i have gutted both of my cats