The exhaust from the headers back has been replaced , both converters and the muffler. and yes I have a snap-on scanner and it had several misfire codes and two transmission line pressure codes. I had the tranny serviced at my transmission shop and they hooked it up to their tranny scanner and the shift sensors were fine and the TCM was fine.They then cleared the codes. No codes since then and no misfire codes either, but still not shifting under heavy throttle. The DTC codes were PO300, PO302, PO303, PO304, PO307, PO1C9 Line pressure low fault, and PO1C8 also line pressure fault. Of course the PO3 are the cylinder misfire codes. Any more ideas will help keep them coming.