With crank seals that work a 290 sounds about right. I'm running a 290 in mine setting on perfect plug chops. Now our altitudes are a little different so you'll be a might richer than I am due to your thinner air but it shouldn't be wildly out of the ballpark.
Before you go trying to tune a deadspot at 1/4 throttle in, you'll need a carb cap that can be removed... the pilot jet is the most effective influence up to about 1/4 throttle and then the needle is the most effective influence up to about 3/4 throttle and then the main jet size takes over. In reality all three work together to meter the fuel rate but at certain throttle inputs, one is stronger than the others.