why is there spark
 

The rex is down on power and I noticed that when idling when the hood is up, there is a spark arcing intermittently from inside the cap on the trailing coil to the ground post on the coil. I know it's probably a stupid question, but is it just a bad wire?

Not stupid at all. Take the two coil wires completely off and switch them. See if the arcing still occurs. If it does...then its not the wires. Prolly only have intermittent operation of two of your plugs

Bad plug wire or coil-to-cap wire, cracked plug, or could be a really bad cap contact. I can't recall if it's the lead or the trail that goes through the spring-loaded button in the center of the cap; but if that little gizmo was missing, you'd see similar.

It does that when the spark can't get to ground through the normal path. Since it's only happening on the trailing, it's not your block ground.

that was a smart idea to swap the wires. I swapped them completely and the arc is still there on the trailing coil. The trailing wire goes into the distributor cap on the top left. The leading goes into the centre of the cap. Maybe a bad plug or plug wire then? I'll check this. I haven't driven it in a couple of weeks as the boy has had it, but it seems to be running different.

We just installed a subwoofer and amp. The power to the amp goes directly from the battery terminal. I ran an extra ground wire to the car body near the factory ground point on the strut tower. Coincidentally, this is when the car started to act a bit down on power (I thought it was his imagination as his mind was probably blown a bit with all the new found bass inside the car :lol:) I should try pulling the inline fuse on the amp power cable although I don't see how this could be the issue.....

definitely a bad T1 wire. I swapped some plug wires around and when this wire was on the leading plug the car would barely run.

Thanks guys. You came through again.