The straight needle carbs are the earlier version. All of the Thunder Tiger 40/46's (straight needle, and angled needle) are true ABC. From your first post on muffler baffles, the TT's will benefit slightly from removing their baffles, but it's hardly worth it, unless you are racing, or are in need of every last RPM. They also have the same problem as the K&B's muffler bolts breaking, which were often replaced on the TT's with 4/40 all thread, even sometimes before they broke, as a precautionary measure.