Updated spark plugs?
 

I have been using the regular recommended Champion copper 344 spark plugs in my 89 renix 4.0. But I recently did the 703 injector swap and added a rustys air tube and k&n filter. With those mods Is there any benefit to putting in more updated plugs like platinums or something else. Or should I just stick to the Champions?

No, stick with what you have.

This. 4.0's dont take kindly to sissy rare mineral flame throwers!

I've run Champion coppers,autolite platinums,NGK,and NGK iridiums. I always seem to run back to NGKs'. If they still made the original DELCO rapidfires I'd use those though.

Champions are good. NGK's are better. Ignore the rest of the spark plug market other than those two brands.

There are only two things a sparkplug has to do, light off the cylinder, and continue to do so reliably for a decent period of time. If the cheapies are getting that done there is nothing further to gain.

AND be in the correct heat range so the cylinder doesn't light itself off ;) For best results stick with the cheapies. Fancy stuff often isn't correct for our engines.

Yeah thats what I figured. I put Bosch double platinum plugs in my ex wife Saturn once, and they were yhe crapiest plugs I had ever seen. They burned way too hot. They didn't even last long. Anyways, thanks for the input.