I just bought a used 97 f150,was told it needed cats. Replaced them and the y pipe still glows cherry red. disconnected muffler still the same.also I have hardly any throttle response.Any help would be appreciated(4.2 V6)

 

Hi moe67 and welcome aboard
I would start by taking the truck and getting it scanned for codes. Not just memory codes, like Autozone checks for, but engine running codes too. A good scan tool will let the tech watch live data and he might be able to see a problem such as a bad MAF sensor or whatever.
I would also have the fuel pressure and ignition timing checked. Neither is adjustable but both have to be right.