well,as i know,the Tuning Parts limit is not existence，or in other way，this limit is not so easy to reach.
i must say,i didnt use any replace mod,i only use addons,sometimes,the tuning parts fails,its beacuse the tuning parts id which in the carcols.meta and carvariations.meta.
it looks like this
<id value="918" />
when this id got the same value with another mod，the tuning parts failed.
but,what is Annoying，even this id is distinctive，sometimes the tuning parts also failes, i cant tell the law of it，my suggestion is just change it once and once，until u got a Available one.
thas what i know，hope can help u。