Newbs... This seems more of a rant than anything else. You say you have tons of problems, you list one. Not giving you a hard time, but if you are going to challenge us..step up to the plate and swing for broke.
Ask the tuner if he set P0300 Random Multiple Misfire to "no report" and no MIL. Likely that's your only issue. Which would mean, he's not as familiar with 3800's...doesn't really mean much if it runs well.
Questions we'd have for you are which cam (vendor based) or specs if it's a custom cam. Did you change the springs when you put the cam in? What other modifications are on this motor? Rough mileage on the motor/mods etc etc.
Fill us in and we'll zero you in on the exact issue faster than you think is possible.
