If I remove them is my check engine light will come on cuz want to remove them soon to be louder

 

The rears are catalytic converters, and yes some people have had the CEL come on after removal...

There is a chance this is because they clamped them creating a leak or did a less than satisfactory welding job...

OR, the truck may have something wrong with it, running close to lean, rich, clogged, broken or shattered front cats etc etc and the procedure puts the condition over the edge thus throwing the light..

I don't believe a perfectly good running vehicle will throw a light if this modification is done properly...