I want to do the ISR mod, but can't just replace the boxes with another pipe. I was thinking of plugging them with plumbing end caps, but don't know where and how to reroute the one vacuum hose coming from the big silencer box to the intake plenum. Can someone help me with this?

 

Get some pvc pipe and cut it to fit. Then get like a copper hose connection and hook up your vacuum lines to it

 

Where would I put the copper hose connection? Is that just closing off the hole?