300zx

First off i drive a 1985 300zx with 140,000 miles on it. I had a problem a couple weeks ago where my car would bog out when i gave it gas. I brought it to my mechanics and they hooked up a fuel pressure tester to find there was low fuel pressure. They put a new fuel pressure regulator in and it seemed to work for a day or so. A couple days after i had what seemed to be the same problem but it was stalling out at idol which had never happened before. I belive this issue could be something to do with the spark now and the spark plug amplifier was very hot and is starting to melt and crack. If anyone could help me on what they think it might be i would appreciate it greatly.