I have a feeling that I'm going to be directed to the N75 valve here, but I thought I'd take the time to explain what's happening and look for a second opinion, before I start pulling bits off the car.
A very standard ADU RS2 running exceptionally well, starts first time, pulls like a train, no smoke etc. A week ago, I pulled-out to pass a bus on a highland road in 6th gear at about 50mph. Half-way past the bus, I suddenly realised that the turbo had effectively failed to operate!
Perhaps it was just me? I'd been pulling and spooling in 6th at much higher speeds earlier in the day, so maybe I was just going too slow for top gear....... Nope!
I was now driving, to all intents and purposes, a normally aspirated i5 20v. The car went well enough and would rev to 7k quite happily, it just didn't rush to get there.
A few miles down the road, that familiar whoosing tune re-appeared, along with the commensurate grin on my face.
Since that day, I've had a turbo which effectively pleases itself. Sometimes (most times) it works, but occasionally it just takes a wee holiday and the car runs perfectly fine up the rev range, but without the anticipated vigour.
I can't see this being a serious mechanical issue and I suspect the N75 has become eratic. Just wondered if this is a familiar tale to anyone?
A very standard ADU RS2 running exceptionally well, starts first time, pulls like a train, no smoke etc. A week ago, I pulled-out to pass a bus on a highland road in 6th gear at about 50mph. Half-way past the bus, I suddenly realised that the turbo had effectively failed to operate!
Perhaps it was just me? I'd been pulling and spooling in 6th at much higher speeds earlier in the day, so maybe I was just going too slow for top gear....... Nope!I was now driving, to all intents and purposes, a normally aspirated i5 20v. The car went well enough and would rev to 7k quite happily, it just didn't rush to get there.

A few miles down the road, that familiar whoosing tune re-appeared, along with the commensurate grin on my face.
Since that day, I've had a turbo which effectively pleases itself. Sometimes (most times) it works, but occasionally it just takes a wee holiday and the car runs perfectly fine up the rev range, but without the anticipated vigour.
I can't see this being a serious mechanical issue and I suspect the N75 has become eratic. Just wondered if this is a familiar tale to anyone?
There's no loss mid-spool - it's either there or it's not.
Magically, without a boost gauge and without pulling codes, you *know* its not a boost leak. There is only one way to know that for 100% and that is actually testing for leaks:


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