changed the coil and the problem seemed to have been fixed .. but at WOT >10 psi it starts breaking up

changed 2 sets of sparkplugs wires .. so its def not wires ..

put in new plugs .. didnt check the gap - they came from another 4g63.

daily driving its fine . but as soon as i step on it, it breaksup and starts backfiring.

Check for boost leaks.
Make sure you have enough fuel - is the fuel filter new?
Gap is fairly important The disk shaped tool is cheap at Princess Auto & crappy, although not the most accurate it's good enough.

Are they stock plugs or a step colder (BPR7es)?

Or: friend of mine had a similar proble, and I believe it ended up being a screwed up aftermarket fuel pressure regulator, what are you running for that?

Sorry to hijack, but I thought this might be relevant here to ask.

If a turbo'ed DSM has just an intake, cat-back exhaust and maybe some free mods pushing anywhere from 13-15psi, should they be running stock plugs or the one step colder BPR7ESes?

^^^
Stock plugs should be fine. Every car is different, however. Too hot a plug and you'll knock. Too cold a plug and they will foul quickly and you'll missfire.

Experiment with the gap too, between .028 and .032 is a good place to start.

I ask because on my car it came with the one step colder, but I threw in stock ones.

stock fuel system .. ill try changing the fuel filter - see if that does anything

FWIW, I suffered from this for a long time.

As an experiment, drop the gap down to 0.024, or 0.022. See if it improves, or makes no change.

P

You put in new plugs from another 4g63? this means they are old plugs right?

Buy a new set of BPR6ES plugs and gap them 0.28 or 0.30 to make the spark a bit larger.

Also note that the non-turbo 4G63 uses a much wider gap.

the plugs are brand new .. never checked the heat range or gap .. will do it today.

the plugs werent gapped .. their gapped now .. problem solved . Thanks