on my TD, I have a cracked connector between #2 and #3, and I sealed it up to get additional exhaust to the turbo.
when I pulled the airfilter box I noticed the cold air intake has a throttle of sorts... what is it, and how does it open and close? could it be closing in the OP's car limiting the intake of air for the turbo to pressureize?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

That's a somewhat mechanical airflow meter. Airflow pushes the flap which registers as an electrical signal for the EDS. You can ditch it if you've disabled EGR and ARV, but it's part of the structural attachment of the air cleaner.

Sixto
87 300D