[Stefano]

X66 trim has the 1/4 panel spears.

"As can be seen from the table above, the X11 code always includes the first four features: the use of black body sill paint and the use of the trim moldings (rear quarter louver, driprail, and wheel opening). The difference between X11 and X55 is that X55 does not apply the driprail and wheel opening moldings.

From this table, we can deduce that the wheel opening stripes, headlamp bezels, and taillamp lenses were not a factor in the X-codes. The table also show that the addition of Z22 (which eliminates the bright taillamp and headlamp trim, since the Rally Sport lamps are different) has the same effect on the X-codes as Z21.

Going back to the X22, X33, X66, and X77 codes, their meanings are now clear. X22 and X33 codes have the same meaning as the related X11 code, but with an added blacked-out tailpan for X22, and with an added Z28 stripe for X33. The X66 code has the same meaning as X55, but with a blacked-out tailpan. The X77 code has the same meaning as X44, but with a Z28 stripe. Including these meanings in a table covering most of the major trim features for all of the X-codes, and adding in the related Z10 & Z11 codes, we get the following result:" copied from CRG site.