PO300 code serious problem in my Cadillac Escalade, any suggestions??

Question

We have replaced all the spark plugs and wires, the fuel injectors, the fuel pump, the rotor, cap and distributor. The iginition coil was replaced over a year ago and is intact. We have also check the engine pressure and have not been able to find a solution in 3 weeks.
It is smoking excessively and it smells weird but the CAT was replaced a year ago as well. Any suggestions on where else to look or what can be the possible problem??

Answer 1

Do you use 91 octane or higher? from Shell or Chevron?  if not you should try to use it.

you can use also use a fuel system cleaner, like 3M 08963 Fuel System Tune-Up Kit

the injector might be clogged or dirty, if there is no spark issue.