ppd files and printer with 2 emulations

[Teruel de Campo]

I have an IBM 4039 12 R that has (1) ps level 1 (2) pcl 5 emulations. I got the ESP software because the printer driver was included. The ppd file was for the PS level 1 emulation. Even that the file was correct the PS is so slow that is unusable. This is not related to the ppd file but to the printer. I also created a printer using the pcl5 emulation with the generic PCL_5_Printer-gimp-print.ppd.gz. This one works great however it does not use the feature of the printer. The only one I am interested is duplex. Is there a way to modify the pcl5 ppd files and add the duplex features for this printer? Is there any way to "merge" the ps ppd file that came with ESP into this pcl5 generic?   I wish ESP  would have both emulation but...
Thank you for your help.

-=terry(Denver)=-