2 x 16min @ FTP should be achievable with a correctly set FTP. I’d highly recommend reading the Kolie Moore thread to get a flavour of what riding at FTP should feel like.
100% agree with other comments, if you can’t do 2 x 16 then you need to reduce your power until you can complete then and then consider reducing your FTP.
If I were to approach 2 x 16 @ FTP, I would use my LTHR+RPE to guide me through the efforts. First interval I might aim to be a beat or two below LTHR. By the end I might be on LTHR or a beat or two above. I might try nudging up intensity to see how it feels. If it’s sustainable, leave it, if it’s not, dial it back down.