No, they won't work with a b20a3. Its going to cost some $$$ to get decent gains. If you upgrade the cams your need to do something to the stock carbs. From what I understand the there pretty restritive. Webbers aren't cheap.

Depending on your skill level and dearing you could swap on a b20a5 head and keep the carb setup. That way you can get cams and headers. You can use mega squirt to run the ingition system. Hell with the mega squirt you could go FI or individual throttle body.