because they suck... ok to be fair they work well on a street car, meaning not raced. If you want to go racing with them you'll need two. Not hard to tune, they just don't tune well. If you run a mild BB you'll need the 800 thunder.
I've won a fair amount of races in both Pro and N/SS with them. Doug
You ain't alone...
For carbs 'that suck', there sure are a lot of 'em out there kicking serious a$$...
apples to onions. you are running TWO and most NSS guys would LOVE to run a pair of Holleys if they could. In a SINGLE carb configuration a Holley is far better.
Next time you're at a N/SS race look and see how many cars can run A/FX. Mine can with Edelbrocks. Many cars run Holleys and can not even run B/FX. Doug