rough running or RPMs goverened?

[RustX7]

Long story short, I did the upper and lower intake gaskets and put new plugs and wires in my 01 LeSabre and it now leaks less but runs rougher at idle than it did before. Before, idle was quite smooth, and now, you notice it.

In exploring this randomly today, I put it in neutral and revved it up to see if anything weird would happen. At almost exactly 4000 rpms it cut out just like I imagine a governor would. The engine didn't shut off and it seemed fine once I got off it, but I don't know if it would have let me get it to rev higher or not. I didn't want to push it. I'm almost certain I've gotten it up to 4k while test driving after my repairs without a noticeable issue. Is this some sort of sitting-still rev limiter, or is it an exacerbation of whatever's causing my rough idling issue?

[maxwedge]

Governor limted by the pcm so people don't blow their engines!