454 Burb trouble code?

[pismorat]

My dad's 4wd 1999 Burb, when towing our Weekend Warrior, keeps throwing an "engine misfire" trouble code. It happens consistently when the engine hits 4250 rpms (in first gear climbing a steep grade). I'm wondering why this is or what will fix the problem. Also, any tips on squeezing more power out of this 454? Thanks.

 

[Thunder]

So what is the code number? "engine misfire" is pretty vague.

 

[4X4HIGH]

Is this the type that uses a central TBI unit with port injectors between an upper and lower intake manifold? If so the lines to the injectors on the SBC's like this have been known to leak and cause that exact problem.

 

[pismorat]

It's code PO300, it does is consitently at 4250 rpm, it has fuel injection, not TBI. When I run the OBD II it just says Engine Misfire Detected. I'm changing out the plugs this week, but they looked ok to begin with. What do most 454's redline at?