Fading turbocharger boost

When the system leaks, you can create a number of problems. you will have fuel problems for sure. with newer electronics and sensors everywhere it will take longer, but the damage is happening. Most of the damage is from over heating components. sustained high EGTs burn out the manifold, and overheat the turbo. Soon these components will fail. They are just not designed for that type of use.
Over or under fueling is the primary problem.
When an engine runs lean, it will tend to over heat more than a rich fuel mix. Rich mixes dump fuel into the exhaust stream that then burn and generate heat. Enough fuel and the turbo can actually become an engin of its own.

 

My 91 started reading 20 instead of the 36 it used to have. I was empty but it still felt it's normal Ferrari self. So I tapped on the boost gauge while on the throttle and it came up to normal.

 

Low boost can be created by a mirid of things, most of which have nothing to do with the turbo.

Air intake restriction, clogged fuel filters, bad injectors, just to name a few.

 

Generally 28-38psi just depends on what file is in the ecm and a few other things.

 

To add to my above post, while the turbo does make the boost, it needs fuel to do it. Low boost pressures very often indicate a fuel problem.

Turbos don't normally get weaker over time. They either work or they don't and when they don't you'll know it.

Every so often I'll pull the turbo intake hose and have a look. You don't want to see a bunch of oil ( a little dampness is ok), you want to make sure it spins free and make sure it doesn't have enough slop for the fins to contact the housing ( even brand new turbos will have a little side to side play).

 

How many miles on it when you did all this?

 

I once had a horrible leak in the charge air cooler and did not feel any performance change, but I did not have the boost gauge either at the time. The notable change, however, was a significant drop in fuel mileage. It was consistent and below 5mpg. That's what made me discover the air leak.