Advice needed!!! Smoke on one side of exhaust

Hey guys, built a new engine about 2 years ago as follows:

360 stroked to 408
Comp ks671-20 cam. Duration 284/291, Lift .484/.484 , LSA 108
LD340 intake with divider ground most of way down
new edelbrock performer 600 carb (I know it's too small, new one on way)

Anyways, here's my issue. It's run maybe a total of 25 minutes since rebuild, but recently when we've been setting timing, etc. we're getting rich exhaust (unburnt fuel, NOT oil) out of only one side (Passenger) after it warms up, completely normal exhaust out of the other side. Not running H pipe, exhaust straight back from headers. The engine is running/sounding great otherwise. I cannot figure out for the life of me what the problem could be, i'll be pulling plugs/compression testing tonight but was wondering if anyone had any ideas?

Thanks in advance