On my old black/tan GLH Turbo, I had modified it with a very large Isuzu NPR intercooler. It had 2.75" I/O, so I got 2.75" mandrel bent aluminum pipe and used silicone reducers at the throttle body (2.75" - 2.25") and turbo discharge (2.75 - 2.00"). It must have used at least 4 feet of pipe just for the intercooler. For the intake, I used 3" mandrel bent aluminum with a (3.00" - 2.50") silicone transition.
I never had it to the track, but it spooled up faster than ever with a stock TII turbocharger. I suspect the large pipe slowed the velocity down and probably increased cooling (more time in IC), but it still pressurized the whole thing near instantly even though there was way more volume between the turbo and TB.
I did have it on the dyno once and it made 198 WHP/270 WTQ with 14psi. The dyno operator (Brent at PFI) was laughing when the boost would hit hard down low.
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