I've had my turbo system in and running on my '03 ES for about 30K miles now..all has been well..running a mere 6psi. One day last week, I got a bad knock when accelerating ...car was at around 2psi or so below 4K RPM...it feels like detonation, but no backfire/noise/etc..so more like a misfire then anything. Currently don't have a wide-band hooked up so unsure as to whether it is fuel or ignition related. My ideas are that, my ignition wires/spark plugs or coil pack(s) are going bad, MAF is dying or is bad, or maybe fuel pump. The car should not be having fuel problems...nothing has changed in the last 30K and I've had the car on the dyno, made numerous runs, etc...at 6-7psi and never one knock or anything... what are your thoughts on this?