I installed a cheap boost controller, about $10.00 from eBay on my 1981 300SD. I increased the boost from 7 pounds maximum to 12 pounds. Here are some things I did to make it work:

1) I have installed a VDO boost gauge to monitor the boost output. I installed the line in a predrilled and tapped bung in the intake manifold instead of in the ALDA line

2) I had to change the hose barbs in the controller from 1/8 inch to 1/4 inch so that the controller would fin in the hose running from the turbo to the waste-gate. Before I did that, I attached my MitiVac to the controller and set it to 12 pounds maximum boost I did not want to take the boost up to the 15-pound fuel cut off although I have heard of others doing that.

This simple modification has made a big difference in the way the car performs. I had increased the amount of fuel prior to this via the ALDA screw and was seeing some black smoke running down the highway under load. Now the smoke is gone and the mpg has increased due to a more complete burn.