What would cause an almost stock 2000 3.8 engine to detonate?

[ramjetlx]

Im currently working on getting my friend's 2000 3.8 engine back to normal operation. It has almost 90,000 miles on it. Im having a problem with it detonating at higher rpms. Only modifications are a BBK CAI in the fenderwell, dual exhaust conversion to stock GT mufflers and MSD 8.5 Super conducter wires. Would this cause it to detonate? I ran an error code on it and it came up saying the EGR circulation isnt sufficient. Anyone have any adviced on this? The car is also an automatic. Any help is greatly appreciated!!!

 

[Skymarshal]

Try running a bottle of good fuel cleaner through it.

The detonation could actually be "carbon knock", or preignition caused by carbon buildup on the piston domes. The carbon will glow from the previous power stroke, and can ignite the air/fuel charge on the compression stroke. On a high-mileage engine, it's a possibility, especially if the engine has been neglected.

I don't know if the 3.8 has a knock sensor (microphone that detects detonation and retards the timing). Anyone know?