i have a slightmisfire on full boost,also i have a coil pack which has a hairline crack on the tip could this crack be enough to cause a misfire on full boost/throttle?

 

Yes, a visible crack will cause misfire problems. People sometimes see an improvement from changing coils that have no visible damage (yet).

 

They don't need to cracked to fail. Mine looked fine but as soon as the boost was turned up at the remap it started to miss at high boost. If old they start to break down once hot.

I had a really bad miss fire off boost as well which turned out to be a coil pack - thought I had done a piston it was that bad.

Try gaping your plugs to .6 or .5 and see if that cures it.

 

As mentioned above, a cracked coilpack will definatley cause missfire problems.

Make sure you support the coil when undoing or tightening up the retaining bolt - If you don't, the coil can twist as you are nipping it up, causing it to crack.