1985 Pontiac Fiero SE

A large hose would either be for the PCV valve in the valve cover or the power brake booster. No matter what, if it doesn't go to anything, then it would be capped off.
Do you have a vacuum diagram on the car somewher to help you figure this out?

I know its not the PCV because of the vacume diagram but everything else is hard to tell what is what on the diagram. Is there any site that has a vacume diagram of fieros?

I have a vacuum diagram in my Chilton Fiero manual. It looks like the only other large line on it goes to the charcoal canister for emission control.
I can fax this diagram to you if you give me a fax number.

I changed the computer and it seemed to fix the idle but there is still a hissing sound I just need to find the small leak and I still have to time it does anyone have any instructions on how to do that?

My manual says to see the underhood sticker for timing spec. If you don't have the sticker, it is most likely 10 degrees BTDC.
The manual says to hook the timing light up to cylinder #1 plug wire.
Then disconnect the 4 terminal connector at the distributor.
Start the engine and run at idle speed.
Then aim the timing light at the marks on the harmonic balancer/timing gear cover.
If necessary, loosen the distributor clamp and turn the distributor to adjust the timing. When it is set, tighten the clamp and recheck the timing marks.
Shut off the engine, then reconnect the 4 terminal connector.

Before doing this, I always use white chalk, touch-up paint, or crayon to mark the timing marks. It makes it a lot easier to see them with the timing light.