I just received my flowtech long tube headers and offroad y pipe for my 99 camaro ss. The thing i need advice with is the 02 stuff...The manual says I need an 02 simm...I just assumed these headers came with everything. Will it run like crap without them?? they are expensive.

 

I guess I'm asking if the simms only purpose is to turn that engine light off or if they affect performance.

 

it'll run. just get the SES light for catalytic converter low efficiency until you put them in.