Cable ties in an engine compartment, no!!! /ubbthreads/images/graemlins/grin.gif
Actually, they do make some cool "ties" out there, if you look at an industrial site, like mcmaster and such; there are lots of options. I would never run "regular" ties though, as they get brittle, look cheap (unless you use a tool (and/or cut them flush) and turn them away from view, but even then) and when not done right are asking for cut hands and arms. In a pinch, sure, but not for a permanent install...
Same thing with the hold down clamps. My personal favorite are the metal ones with a rubber insert, but they can get $$$...you can make (modify) your own if you're creative though...I've used plastic ones also, but just prefer a better look and more durability.
Speaking of ordering things...One thing you have to be careful of on hose clamps, for instance, is to measure the "finished" OD (the hose spreads over a nipple and becomes thicker overall, for instance), or else they don't fit right. Not so sure the tube hold down clamps would be like that, but IIRC, they always are sized larger than they are.