I found the Kaplan's study manuals to be to be very helpful when I took the Chem Eng FE exam. The questions study guide were harder than those on the exam.
I've since purchased the PE study manuals for chem eng. I have not decicated nearly the time studying for it as I had for the FE exam as I am most likely a couple years out from taking it.
At any rate I would suggest checking them out. I believe I paid around $150 for the study guide, practice questions, and practice exam. We worth it if it gets you a passing grade on your first attempt!!