i recently removed the whole aiv system off my 91 240sx super hicas and it seems to have lost top end power. i made sure to plug the two small vacuum hoses off the bottom, plugged the pipe that came off the manifold, and plugged off the top that goes to the air filter. it seems like it takes it forever to start building rpm after about 4k i’m not sure what could cause this and i really don’t wanna put the system back on because it takes up so much space. someone please help

Hey, welcome to NICO Club!

Perhaps your AIV delete didn't get finished properly and you have a vacuum leak or a computer issue? We have a great write up on the delete, but it's for a 300zx. So, you'll have to 'translate' that to your car. We also have the FSM for your car and you can use that to help identify connections and locations of stuff that might be different from the 300zx instructions. Here's a link to each of those and I hope they help a lot. Please let us know if you need further help so we can reply or if you get it fixed so that others can benefit... either way.

Write up: http://www.nicoclub.com/archives/remove ... s-aiv.html
FSM: http://www.nicoclub.com/service-manual? ... 1991_240sx