1. If plug wires are blowing out, could be a leak past the valve cover seals.
2. If John tuned it, I'm sure your timing is OK or he would have said something.
3. If you jumped your compression up significantly and you are on the stock cam, that could be your main power issue. Cams and pistons should be viewed as a package. You can lose power by your engine working against itself with high compression and too little cam to bleed off compression. In short, your motor may be straining to put the squeeze on the air/fuel, killing crank inertia and robbing power. This is why dynamic compression is a more important number than static.
Longer duration, bigger lift cams will allow some compression to bleed back into the intake on the compression stroke.
Think of it this way: you don't boost compression to get more compression for its own sake, you boost compression because you need more of it to run bigger cams. You left that part out of your upgrade package. Your engine is saying, WTF?