At full throttle/full boost the car putters, looses all sorts of power and violently shakes as a result of whatever is going on in the engine. The turbo does this stutter, its almost like the engine quits for a second comes back, quits again and so on unless I let off the gas. This first happened a few months ago and it was because of a malfunctioning spark plug and a misfiring piston (I figured this out because my check engine light was flashing at me and I read the code). Needless to say, I replaced the spark plug and my baby was back to normal. About a week ago, the same thing happened and I immediately thought that perhaps my spark plugs (NGK Iridiums) were being funny again. I replaced them and made sure my gaps were set properly only to find that my problem was not fixed. I'm thinking that because my check engine light wasn't flashing and because replacing and tweaking the spark plugs didn't change anything, perhaps there is a bigger underlying problem. Is my turbo toasted? What are your opinions? Any feedback is greatly appreciated!

A few things you should know:
1) The car has 130k miles on it.
2) I sent my ECU to get remapped by Nick Taliaferro and his team from Genuinesaab about two years ago. It's safe to say that my turbo has been "working hard".
3) The car is a 2004 9-3 Linear