No, you always can use the same number. And I suggest you doing so.
I think 180 is more than enough for any car. Also, for best results you must manually adjust ALL the elements, and my tool doesn't support it anyway, so it doesn't matter how many elements are used.
Is there negative consequence for using more than that? GIN_Murcielago.gin has 180 elements. When reencoding I tried:
180: I had the same issue I was having earlier.
184: GIN_Diablo.gin number of elements. A bit better.
195: Worked correctly, but I agree that you don't need this much, I just threw in a high number to see what happened.
I insist that depending on the sound you may need more or less elements, because it's very hard to bend the sample's pitch exactly like the original sound, so the most you can have is an approximation. 180 may work if the approximation is good enough, but this particular car (Murciélago) was not the only one I had problems with. When reencoding the sample extracted from GIN_Ferrari_360.gin to replace GIN_Gallardo.gin with, I had very similar problems, which don't happen when you simply replace GIN_Gallardo.gin with the original GIN_Ferrari_360.gin, and this is important since both sounds have very close top end. (BTW Gallardo with Ferrari exhaust sounds awesome!)
I've been having some fun with your tools lately but haven't made a "right" sounding bank yet, due to procrastination.