Seafoam wants to be sucked into the Upper Intake Manifold. The best access is the brake booster vacuum line. Take it in only a little at a time though...if you take in too much at once you can fill a cylinder with the liquid, hydrolock (solventlock?) and bend a rod
You do NOT want to induct seafoam at the mouth of the TB, as it may damage your MAF sensor. The TB wants to be removed from the car and carefully cleaned by hand so as not to damage any sensors. The bore and plate can be cleaned with a toothbrush and carb cleaner; the MAF wants to be cleaned with a special MAF-safe cleaner like this:
2004 Buick Lesabre Limited, Gran Touring; Bone Stock
1998 Buick Lesabre Limited, Gran Touring; Mods: Poly sway bushings/endlinks, Tru-Cool trans cooler, Thrasher shift kit (med), PLIM, front PEM; Mods in progress: Alot of stuff, but slowly...