• Check or replace all vacuum lines going to the ALDA again with focus on the small rubber pieces that connect the lines. Sometimes clogs are difficult to determine. The boost signal/pressure must make it to the ALDA.

• “T” a boost gauge line and boost gauge right at the line going to the ALDA or the line into the intake manifold. The gauge is cheap and can be invaluable as you make changes. Just do a “test run” on a highway ramp or up a hill to measure boost changes under load.

• Blow out the ALDA and the line going to the intake manifold. Sometimes these get filled with gunk blocking the signal to the ALDA. GSXR has tons of photos and of the ALDA which can be helpful.

• Pinch off, or block completely the actuator hose for the waste gate. (with the boost gauge this will provide feedback so you don’t over boost) With the actuator line blocked you should get max boost out of your turbo at about 2000-2200 RPM.

• Do you see any blow by signs around the manifold. New black oil? This would indicate leaks in the crossover pipe or your manifold. This could be causing boost to “leak” out, but it would have to be a big leak.

• If you drive along a concrete divide or wall with your windows down you should be able to hear the turbo spool up. High pitched wine just like a 18 wheeler. You should be able to hear it whistle as it starts to spin up before 2000 RPM.


I had a poor performing turbo and was able to get about 8-9 psi of boost out of it with the waste gate forced shut. This boost level was also not sustainable as it would quickly fall to zero with slight release of the accelerator. The turbines were chipped and torn up and it didn’t spin freely. To get it to this level I had to check everything including leaks and cracked lines and plugged lines. I also blocked off everything under the air cleaner, eliminating it from the system. On this turbo I had to hit about 3000 RPM before any boost came on at all.
I bought a used turbo on ebay in perfect condition and replaced the old one. This made all the difference in the world. Now it boosts quickly at 2000 RPM. I have it set for 12. At highway speeds it provides constant boost at about 5 or 6 and the slightest blip of the pedal brings it to 10-12 quickly. With the old turbo, I had to "work" or force the car to boost and with the new turbo it responds like a dream and it accelerates much much faster.

The test where you strapped the vac/pressure gauge to your wiper blades and then “got on it” to 4000 RPM and only hit 6 psi of boost sounds identical to my problem above. It sounds like to me that this is all that this worn out turbo is able to give you!

There are some threads about rebuild kits on the forum that might be worth checking out.

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