[Supras] Lexus Problem

[Bob]

Are there any Lexus experts out there?  

I have a friend with a shop that I owe a favor to.  He has a troublesome 95
SC400 in the shop with an intermittent hesitation on acceleration.  The shop
has cleaned the throttle body, injectors and tested the tps.  Ignition and
cam timing is dead on and there are no codes in the computer.  According to
the scanner the knock sensor(s) randomly go off and retard the timing.

The car is running 94 octane and yet still the problem is happening once in
a while.  I know that Supra's and Mr2's have had some problems with the
knock sensor.  

He would toss in a new knock sensor as a guess but they are buried under the
intake so this isn't a 5 minute job. Testing this sensor is very difficult
since he doesn't have a Toyota break out box.

Any suggestions?  

Bob