Carb up engines run hot = failing on nox. This is a HC = unburnt fuel and CO = rich burn issue. A tune up isn’t going to fix it. What with the phase "just a tech’s $0.02??? Feel special?? Warm and fuzzy inside??? Suggestion that are wrong, is like the tech that doesn’t diag properly and wastes customers money. Retarding the timing will also not fix this issue. Retarding the timing = later burn = cooler temps = lower nox levels but higher HC’s levels due to the later burn.
JUST A TECH’S $0.02