Can you post photos of your setup? It sounds like you have too much preload between the booster and master cylinder. Below is a stock pushrod and you can see the adjustable part at the end. It appears as an acorn nut in the photo.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.