Ok I have a 97 tocama with the 3.4 i just had new head gaskets and seals put on. Now everytime i start it, it will idle rough and sometimes almost stall. I noticed when i am ideling for awhile the check eng. light will start flashing. I took it to advanced and had them scan it, came back with cylinder 6,4,2 misfires and O2 sensor malfunction. I am at a loss, any help would be greatly appreciated