When you get a crit from a weapon that has an ammo type that makes you make more than one save, can you use the symbiomate to avoid the extra armor saves applied by the type of ammunition?
No, because the extra rolls are part of the Critical. However, when using the SymbioMate, all Critical Attacks received will be applied as usual. The effect of a Critical with, for example, EXP ammo: Critical hits with Explosive Special Ammunition cause the target to lose 1 point directly from his Wounds/STR Attribute, bypassing the first ARM Roll (the target must still make the remaining two Rolls).