I would recommend at the very least a compression test; a full leak-down test better still.

 

Thanks ill do a compression test and go from there thanks for all your input and advice

 

Double-check the cam and spark timing. Very-advanced spark was mentioned before, but now that you say premium fuel gives better MPG - a very advanced spark might cause that to happen.

But 1996 is OBD-2 so it's a bit curious how the spark can advance that much. I don't think there's enough adjustment in the TDC sensor.

 

Ok will do thank you for help