3+ yrs ago I bought a this carb from a local TC member after he went EFI on his 700hp 540 in his 71 Chevelle, I used it WO any changes on my 489 when we dynoed the engine and after installing the engine I adjusted the carb with a vacuum gauge and a few months ago put an AFR gauge in the car and it shows it’s way too lean, where to start? checking floats then adjust the 4 corner mixture screws or just rely on what the plugs look like?