I had a 79 Z28 also. There was no ECM on these cars until 82 from what I remember. The engine ran richer than a fuel injected car. That is why they got less gas mileage. With the emissions and ECM on the newer cars the fuel management system leans the engines to make best fuel mileage along with performance being secondary. The fuel injected cars have less leeway for running to lean because the computer control what you can do with the stock system. So that is why the knock sensors are needed. If you took them off and the engine gets to lean them you are going to burn the pistons. You should put a FPR on your car and adjust it to about 46 to 48 psi. That way you will not go lean unless you have a injector or pump problem. If you still are getting spark knock then it could be wires, plugs ect. i don't know why your car is running out of power at 5600 RPMs. My 96 WS6 has the rev Limiter set at 6100RPM. It pulls to 6000 were I shift. The only mods I have is B&B TriFlo,K&N,160 stat,Air Foil,Frame tied,373 gears and HPP3. You should check your tach and make sure it reads correct if all else is ok.
I can remember knock sensors being on GM cars all the way back to the early 80's on some GM cars and trucks. I was working on a GMC Van that had no power above 3000 RPMs. I could not find anything wrong with anything. I ended up replacing the carb,cap,rotor,wires,dist,ect. Looked for plugged cat converter. Still would not pull above 3000 RPMs. Took fuel pressure reading they were good. I finaly found out the fuel pump arm was rattling causing the knock sensor to retard the timing to the point the engine would not make power. I didn't make any money that week because it took so long to fix that truck.

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87 IROC L98 700R4 A few mods. Best et 12.96 at 110 mph
All motor No NOS or Supercharger.
96 WS6 FORMULA Best et 13.5 at 105 mph

[This message has been edited by Chris Ja (edited August 31, 2002).]

[This message has been edited by Chris Ja (edited August 31, 2002).]