From 2003 Workshp Manual:

Component Description
NFEC0932
The knock sensor is attached to the cylinder block. It senses
engine knocking using a piezoelectric element. A knocking vibration
from the cylinder block is sensed as vibrational pressure. This
pressure is converted into a voltage signal and sent to the ECM.

During the following conditions, the ignition timing is revised by the
ECM according to the other data stored
in the ECM.

At starting

During warm-up

At idle

At low battery voltage

During acceleration
The knock sensor retard system is designed only for emergencies. The
basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry
conditions. The retard system does not
operate under normal driving conditions. If engine knocking occurs,
the knock sensor monitors the condition.
The signal is transmitted to the ECM. The ECM retards the ignition
timing to eliminate the knocking condition.

Al Moodie.

get the ECU codes read.

could well be a failed knock sensor.

and how did you have the throttle body cleaned? If you did not have it
done using the specific highly specialized solvents, you may have FUd
that up.

Possible failing MAF sensor ,,,,will lean out the engine enough to
cause spark know that can not be compensated for by the ecu and knock
sensor..soon you should start getting Lean bank 1 or 2 ECU errors.