Bit of an odd one. 1995 BPU Jap Supra, running in current configuration for years.
When the car is started from cold and I take it for a run everything is fine and it boosts strongly as expected to over 1 bar, however boost disappears if you end up in heavy traffic or park the car up for 30 minutes. Opening the bonnet to let the heat out helps when you park it up.
So far I've replaced the vacuum lines and ruled out boost leaks, although not sure why that would only be an issue when the engine bay is heat soaked. I've also recently replaced all the VSV solenoids as the IACV went faulty last year and there was no boost from the second turbo, I replaced the EGCV and EBV solenoids as preventative maintenance at the time too.
I don't think the issue relates to the pressure tank as there are no issues when there is no heat soak in the engine bay, and I'm only seeing 0.1 or 0.2bar (so does not seem to be an issue with the sequential system). When the issue occurs, If you manage a few miles at a reasonable speed to get some airflow through the engine bay, boost starts to come back, and oddly modulating the throttle around the midrange seems to help boost pick up - albeit to less than usual ( 0.8'ish bar).
I've a suspicion the rubber corrugated turbo link pipes might be the issue, collapsing on the inside and choking the intake, more noticeable when the engine bay is hot and the pipes may be more supple:
Is there anything else I should be considering?
Thanks,
Jamesy