Here are the things i would check and in order...
1. Check for exhaust leaks.... take a towl put it over the tail pipes and look to see if you have any exhaust leaking with the pipes....
2. At the charge tube to intercooler connection, again run the engine, plug the charge tube and find a smoke device of some type and it go through the intake on the tubo,, again look for leaks......
3. The base of your T tubes can have a good seal with epoxy,, but if the connectors to the line have small leaks, you will run lean.... sometime "looks" good is not enough... redue the top seals again.... for me i use hard poly boost line and put inside the 1/4 inch line and use safety wire to seal up.... more than one time it took several attempts to seal up the vents right when by looks i thought they were ok and they were not...
4. Check the hard fuel delivery system... line presures and kinked lines....
5. If you have had it up to your hears and are readay to give, don't... go out spend the money for a recording 02 sensor.... it will tell you lean or rich....
6.After that, take it back to Jeff, bet he will find the problem quick...