I have used Seafoam occasionally in my 1994 Grand Cherokee. The way I have used it was to feed 1/3 of a can by using the vacuum suction line that normally goes to the master cylinder. I would feed it until the engine died and would let it sit for 5 min before starting it up. I did noticed it seemed to idle smoother for a few weeks.

But I more enjoyed the white smoke that would make neighbors think the house was burning down

I also have a Mercedes-Benz CLK430 (MY 2000) and have never used Seafoam on that, since I always put good gas and kept up the maintenance regularly at the dealer.

Doubt you'd need it in the E70, which will hopefully replace my Jeep later this year when the 2010 arrives