Changing your plugs heat range to fix a problem is an old timers trick and not recommended for an engine you'll want to be reliable. Find your problem and fix it right. I gathered from your plugs readings you're going lean, which would be accurate from your first post stating you're getting a pop which indicates prefire usually caused by a lean mixture. Here's a list of things to check out:
Fuel Pressure - Self Explanitory
Compression - not likely an issue, but always good to check.
TPS - Shoud show continuity at idle and none off idle
O2 - Not sure about the ECCS in the turbo, but I know the N/A ECU has an LED on it that blinks with the O2 readings.
CHTS - Cylinder Head Temp Sensor, cheap replacement part and try wiggling the connector and wires, the old electrical could be shorting.
Timing - If the timing is off of course it won't run right.
I'm no turbo expert, but that's where I'd start.