The plastic would need to resist atleast 200 degrees IMO (If not more) with out becoming pliable.
I know PVC piping is not suitable. I do not know any specs on the thermosetting plastic you brought up? Would be good to look into!
Would also be nice if we knew the inner diameter of the upper intake as is??? (largest - dual honed SVT ~ actually any would be a start!) Give a starting point of reference.
2" = 50.8mm - I'm thinking that's pretty big intake runners...
The "pleated" venting duct would kill air flow & velocity. Ribbed for her pleasure is not always the best design...
