I have searched and did not yield any results but unless I missed something, please feel free to post it.

Here's a quick run down...

When I am driving and the car (SC400 93) hits 1500 rpm the check engine light comes on and the car goes into a sluggish mode after that. I talked to a mechanic and he said it sounds like my knock sensors. He said that they come into play around that rpm and since they went bad then the ECU goes into a safe mode with the car and that explains my poor performance and low mpg.

ALTHOUGH when I turn the car on and rev the engine up to 2500 rpm quickly and then drive, the car remains fine and the check engine light does not come on. I am at a loss here and am not sure what to do...

He quoted me $900 to fix it. $370 for parts ($175 for each detector) and then $450 for labor (at a $90 per hour basis). Is this something that I can do by myself if I have the parts even though the sensors are in the engine? I'm just lost guys and ANY help would be greatly appreciated! BTW This is why I love this forum. Good guys who can sympathize and offer great advice. Thank you!

 

you can do one by yourself, and the other just might be a bit of a pain, but you can also do it. I'm unsure of OEM prices on the sensors, but used they are generally VERY cheap, so that seems a bit much.

This is on a 1jz, but i'm guessing the 2jz is very very similar to where the rear knock sensor is just a 24mm(iirc) and a extension away. . .
the front sensor required removing one of the belt-driven parts and a brace behind it = a bit more work.

 

^He's got a 400

They're in V of the engine, under the intake manifold.
While he's in there, get him to do the starter contacts. Massive overlap in labour between starter and knock sensor.

If you aren't mechanically inclined at all, don't even try something like this as a DIY yet. Hope your guy knows what he's doin'