I can tell you that even with the needle valve detached from the back plate and attatched to the firewall, it still gave the same results. I did not get the new needle but did cut the old one off the backplate, so I think the problem is with the needle valve itself. I put the 61 super tiger carb on and now it is running good. It will sit and idle for 5 minutes at 2400 rpm and then jump right up to full throttle when prompted. Mid range on the ground sounds smooth but for some reason in the air it just sounds funny. Maybe it is just the sound the stock muffler makes.