New to this 1990 454ss
 

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1990 454 ss 137,000 miles. Well had it for a few years I'm having a engine light ,fist was the knock sensor now I have code 42 and its talking about the ecm being bad but all is doing is running rough and smoking if I advance time to like 12 deg runs a little better I will change distributer tomorrow and suggestions ??? Thanks

Mine done this years ago with the stock tbi engine and it was the distributor causing all the issue with it.

Holley Terminator, 950 CFM fuel injection system on a GMPP open plenum manifold, with a WlBro 255 LPH in the tank cured mine.

Sweet ride!