2g - poping sound @5k rpm help please.

[Pameluxen]

Hello, I've tried searching many places over the internet and habe had no luck in finding a solution to my problem. My experience with forced induction cars is limited.

What happens is, on my 1998 eclipse gst - at 5-6k rpm at wot / any more then 50% throttle Im able to hear the turbo spooling, i don't go anywhere, and when i hit 5k rpm a loud poping. sound happens.
The stock boost gauge reads full; i brake boosted the car and the wastegate actuator is not actuating.
did a vacuum test and it held steady vacuum so no leaks.
I did a tune up and noticed that the plug cylinder 4 had pieces broken off. So if I'm not mistaken the popping sound is detonation?

I've been suffering from this problem for months now, I'm not sure exactly what it could be. Any ideas?

The only mods are:

K&n filter
3" exhaust straight pipe
Its been a while but i believe if i remember right i put a 255? Lph fuel oump
and i have no idea what turbo is on it, i got the car for a steal and it barely ran so i took it to a local shop that did work on mitsubishi's. The car was all stock (that i know) except the turbo and j pipe. A friend of mine said mine looks a lot like a disco potato but im not too sure.

Any help is appreciated.

Thanks.

 

[2g_turtle]

Change the plugs they might have fouled out, you said you seen #4 broken, it sounds like detonation to me, I wouldn't keep driving like that.

 

[meliketoball]

Change the plugs they might have fouled out, you said you seen #4 broken, it sounds like detonation to me, I wouldn't keep driving like that.

I agree. Get NGK BPR6ES's.