what is this part
 

i have been running a mp with the air pump there and spinning but with it disconnected for yrs. i believe this either went to the air pump or the intake. i think at one point it was capped though. should it be? i noticed that on decel it shoots air out...almost like an exhaust leak. when giving it throttle though i dont "think" it sucks in. does it have somehting to do with the acv?

i just did some searching and i found that it is the hose from the acv. i guess i should have searched but i got more questions. with the airpump disconnected and just sitting there(i will remove it someday soon actually) should i block this off some how (with a block off plate somewhere or a cap ). when u guys remove your airpump what do u do with the acv system?

A lot of people just cap it off. There's a thread about it using table leg caps from Home Depot. That's what I did.

Yup, i used a table leg rubber cap and drilled like (4) 1/4" holes in them.

When removing the airpump, the ACV become useless. You can just cap off the hard lines and be done. However, the cleanest thing to do is to remove the ACV when removing the airpump.

i am unclear what i need to remove the air pump. do i just need that idler pulley? or do i need the greddy one as well. like this : http://www.rx7store.net/product_p/greddy%20pulley.htm

i dont understand why i would need the greddy one. my understanding of the idler pulley is that its just a bracket with a pulley at end of it and lines up literally right where the ap would be. is that wrong?

that air has to go somewhere though doesnt it?

You can either use a Greddy (or similar) Pulley kit or an idler pulley. Using a pulley kit does have some benefits. The pulleies are larger to create better contact between the pullies which also underdrives them (to some extent). This helps with high rpm cavitation of the water pump.

With the airpump removed, there is no air.

there is though. the par tint he picture shots out air on decel.

If there is no air coming in (i.e. airpump removed), there is no air to expel. That is the airpump relief line which works like a BOV for the airpump. If you remove the airpump, there is nothing.

well then i got a problem some where as this thing DOES shot air out.

Once again, if the airpump is removed, cap it. If you still have the airpump attached, then you need to allow it to vent.

+1. I used a 7/8" or 22mm, rubber cap