You must have two things to get more power with a turbo -- more air (from the turbo) and more fuel. If the boost line from the intake manifold is leaking (or the switchover valve for over-boost protection leaking), you won't get more fuel, hence very little extra power. Check the boost signal line for obstructions and integrity.

If the signal line to the vacuum amplifier isn't connected, the transmission will get the wrong vac signal and shift funny -- and may slip badly on shifts, causing it to fail prematurely.

Your lack of power brakes can be a loose vacuum line or a booster full of brake fluid from a leaking master cylinder, or a bad vacuum pump (the check valves fail, or the cam is worn out).

Get a Mitivac hand pump, it has a convenient guage on it. You must get at least 11" of vac in two or three minutes idling in the main vac line -- if not, you have a major leak (which can be the booster, although I've not every seen a bad one on a Benz yet), or a cracked line, etc. That Mitivac is handy for chasing down and fixing other leaks as well, and works nicely to change the fluid or bleed the brakes.

I believe there has been a vacuum line diagram posted for your car here on the forum in the past, do a search, it will make life easier.

Peter

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!