I've seafomed my firebird before, via pcv, tank, and also ran it through the crankcase as instructed before an oil change. Seemed to alleviate a sticky lifter for a while.

The LS1 engine fbodys usually report good things from seafoaming, as do the v6s but my heads must have been relatively clean, since I did not get a lot of smoking.

I cannot imagine needing to run this in the gas tank of a lower milage x5, given they require high octane fuel in the first place. I would consider running it in the crankcase itself before an oil change.

It is useful if you are checking for leaks though: dump in seafoam and watch for the smoke. Anything besides the tailpipe is a leak.

Also bear in mind seafoam is not an octane booster, it is from what I remember, a keytone. "Techron" or similarly branded octane boosters do not do all of the same things as seafoam.