ThirdEye

Hi, I have some questions regarding the timing off my car and was hoping someone knowledgeable could answer a few of them.

Last May, while coming back from a snowboarding trip my car broke down on the side of the road and was heavily misfiring. It turns out that the tip of a spark plug broke off and got sucked into the combustion chamber. This was very mysterious and I could not figure out why this happened. I had the head rebuilt and the car has been running good so far except between 1500 and 3000 RPM is chatters. It's not too loud but its definately noticeable with the windows down. I was thinking that this might be due lifter noise and I am doing an oil change on Monday with some Justice Brothers Engine Tune-Up. The thing is when I opened the hood and opened the throttle body manually I could hear it coming from the back of the engine bay. I thought it might be the lifters still as it is pretty difficult to pinpoint but today I read that a bad cam tensioner will make this noise. Is there any easy way to diagnose this? Now, I just had the head rebuilt and I had the cam chain and tensioner replaced. However what I do remember reading was that a spark plug broke off in another AW members car and that he believed it was because his timing was off by a tooth. I also happened to replace my timing belt approximately 10 months before the incident occured and was wondering if there is any way to check whether the timing is indeed off. Now I do not know too much about the internal mechanics of the engine but with the head off, wouldn't the mechanic have to have realigned the timing? SOrry of all the questions but I just spent $3000 repairing my car and now I am worried that something may be wrong again, and I do not want to have to rebuild my head again. Thanks!