Idiling Question

[Renesis]

When i first got my car I noticed it had a bad idle. It would literally kick back in before it died, when I sat in neutral. I took it to the shop and they told me that I had a cracked engine block and within a week i had a reman-engine installed.

I noticed today that my idling is really rough. I sat in a drive thru in neutral and it began to shake more then normal and really sound like it wanted to die. It did it a couple times but always quickly kicked back in. It's hard to explain. But basically it was quite loud and would just go low to high. There are no loose wires nothing missing. I'm hoping that It's nothing major and maybe just something the rx8's do. I was wondering if anyone has the same issues or if this is normal.