JR, you might want to consider limiting (if not cutting out completely) your caffeine intake. I had a similar situation (that occurred several times) where I thought I was having a heart attack. The doc finally caught it on EKG and it turned out to be something called premature ventricular contractions. I was drinking 3 diet mountain dews a day plus a couple of cups of coffee. I cut out all the caffeine and it hasn't (knock on wood) happened since.

'06 TBA - Black, AI and Snorkel removed, K&N Drop In, Gutted Stock Pipes, 145/42, 2 turns out.