It will start and run poorly if you give it about half throttle. The only code in the PCM is code P0300: multiple cylinder misfire. It has good spark, 60 psi fuel pressure and 160+ psi compression on all cylinders. I have put a smoke machine on it looking for a vacuum leak and did not find any.

I have also checked the exhaust back pressure and did not find a problem. When it does start the exhaust smells rich. Data stream readings are not showing any that are way off. Has anyone else seen a problem like this?

Thank you for any replies.