Likelihood of PCE model ouput

I know I can use a my_PCE model as a predictor:

YPC = uq_evalModel(X)

I am also interest in the inverse, i.e. in finding the likelihood that a given Y could be produced by my PCE model: L(my_PCE|Y).

I read the user manual but I did not find something useful.
Thank you very much for your help

Thanks for your attention, I did it.