It sounds to me like you need to increase your main (front) metering jets a
couple of sizes. If, for example, there are 64's in there now, increase at
least to 66's. First, though, check the front float level to make sure it
isn't too low, which would also make it run lean. The fuel level with the
engine hot should be just level with the bottom of the hole. It is very easy
to misadjust the float level. The rear jets should be six or eight sizes
bigger than the fronts. Re-check the rear float level too just to be safe.
You can do it either with the engine idling, or turn it off and check it if
you're afraid of fire.