I add a can of Seafoam every other oil change. Where I do know Seaform works is in cleaning the fuel level equipment. With my M35x, about every 5000 miles it would not fill completely up and would not read full either. I would add a can of Seaform and before I needed to fill up again, it fixed the problem. I haven't seen the same problem with the Q70, but I add it anyway. I guess that I figured that if it was cleaning the stuff in the tank(s) so well, then it might be helping with the rest of the fuel delivery system.
I agree with what Larz says in terms of sticking to OEM parts, too, but I'm not 100% OEM. I like Brakemotive brakes better than the OEM ones, both for looks and stopping in the rain. I also purchase Wix oil filters, where I used to buy the Nissan ones religiously. Finally, I've replaced most of my smaller bulbs with VLED bulbs and they look 100% better than the ones that came with the car.