Just to keep things off topic.......

I haven't had a B1BS in the shop in quite a long time.
As I recall, ootb they did flow close to 290...... But didn't get near that until .700 lift.

One thing I remember about the first one I tested was, the low/mid-lift flow was so bad I stopped about 1/2 way through the test to make sure there wasn't a problem with the bench.
I couldn't believe that an aftermarket head with a 2.20 intake valve could be that bad.

I ended up getting them to work pretty well...... Around 320@.700 while keeping the runner fairly small, and making some nice improvements in the low/mid flow.

On a flat top 446 in a 3900lb car they were good enough to let the car run high 10.40's with a single 850, and high 10.20's@130 with the MP TR and 2 x 750's on it.