Hello,
My c420 also came with broken air lines so your not the only one. I love the engine so I'm just going to glue them back on using a toothpick. I haven't had a chance to run it much but it seems "jerky" until it reaches speed. I'm using bluetooth so maybe it's a momentum setting, etc but also could be other factors, dirty track, power loss, etc. I really haven't had time to investigate. That being said....this thing is gorgeous.