Did replacing your vacuum lines really make that much of a diff?
 

The title pretty much sums it up. I've read that replacing the vacuum lines on the 44s can make a world of difference. Is this really the case? The lines are 21 years old now and I'm considering replacing them relatively soon.

So much of the FI is driven by vacuum readings, it can make a huge difference.

Gotcha, FI is uncharted waters for me as I'm used to the good ol' carb. cars. I think I might just go ahead and order the hoses now. Approx how much of each size do I need to get to do my entire 84? TIA

If you don't have a single leak in your system then it wont do anything. If you have air leaking then it will make a world of difference. If you have 20 years on the OG lines then I am guessing it is a good idea.

I would measure your vacuum first. I think ~18 inHg at idle is good. I got 13 inHg and car runs beautifully though - most of the time. Idle drops perilously low every now and then and has stalled twice last winter. That's my ISV, I think. But as long as I'm under the intake manifold I'll replace every vacuum line and hose I can see.

What are some symptoms that vacuum loss would cause? Poor idle? Poor throttle?

The lines for the damper, fpr, tb, all are 4mm lines using 3 way 4mm tees. 20 ft will do. 5-6, 3 way tees

The hoses in the AFM/ ISV and etc are varied sizes from 10mm to apprx 13mm ID. 1 each and are molded hoses. Look at the hoses for proper bends and lengths.

I just replaced all my vacuum lines. before she was missing at around 4500 rpm, rough idle, poor gas mileage. I also changed plugs,wires, cap & rotor. Now thanks to the guys in here for their help. She runs great now.

Looking for a little clarifcation here please. Can i replace both the soft rubber connectors and hard vaccuum lines with a 1 piece run of silicone hosing? I'm referring to all the small 4mm tubing.

I changed all my lines with vacuum lines from the local parts house. I do not know if the diameter of the line is critical or not. Mine seems to run fine though.

Yes....The hard plastic is to help with heat created so the hard plastic lines were installed to prevent the hoses from melting as they rest on hot metal particularly under the intake.

I ran all silicone and zip tied them up and away from any contact with hot metal. What you are dealing with are a bunch of rubber elbows attached to plastic tubing. All you need to do is cut new line to replace the plastic. I found that most of the cracks were in the rubber 3 way connectors(tees).