What about:

Firebird: the highway to [reliable] performance.

or better yet:

Firebird: your highway to [reliable] performance.
[] denotes with or without of course ;)

'your' instead of 'the' is better because with this the slogan addresses
the reader directly and thus grabs his/her attention quicker.

Still, not perfect, not bad either (ahum) just another idea.
I think when the right slogan comes, we all know it. So let's keep on
trying.

Dennis