Ok I'll try to keep it breif and give as much info as possible. The other day I start the car for the first time in about 2-3 days and it started up and started idling realling rough. The car start shaking and everything. I didn't happen to notice what the rpm are at but I did open the hood to see if I noticed anything off the bat. It took about 2 minute but the car settled down and started idling nicely again so I'm hoping it was no big deal. There has been a knocking noise lately coming from the engine bay but I thought it was normal if your not running the 91 octane or higher. I also noticed a rip on the under side of the intake elbow in the area where it connects to the TB. This could be the start of my problem but I would like some input before I get start. Thanks for any help. It's a 1995 z28 with 140k miles

 

Replace the intake elbow. Unmetered air (air not flowing through the MAF) is giving you the wrong air fuel ratio causing it to run rough.