I've had that symptom several times. Idles fine, but dies at full throtle. It usually turns out to be a hole in the fuel line between the tank and the needle valve - an easy fix. I had one airplane/tank that had a rough spot where the hose had to make a turn to clear the motor mount. I deburred the brass tank tube inside and out with an X-acto blade and haven't had a problem since. That line takes a lot of "abuse" being pulled and replaced to fill the tank.

Only takes a tiny leak to kill the engine. When diagnosing a problem: start with the easy fixes, then move along to the inexpensive fixes.