engine cuts out while cruzing

[smilenpsyco]

I'm having a problem that has me stumped, hopefully someone with a lot more knowledge about the car reads this and can help.
I've got a 98 Cavalier, 2.2 L with a manual transmission and 157k miles that i can feel it cutting out or missing only when i'm maintaining a speed. I feel it a lot more going downhill, but it is definately there when i'm maintaining 55, 65 or 75 mph. It doesn't do it when there is a load on the engine, like when i'm accelerating or going uphill, only when i'm maintaining a constant speed.
I've checked my plug wires, all look good. my plugs are platnum and have only about 40k miles on them. At my last oil change I did an engine flush, and changed my air and fuel filters to no avail.
Has anyone ever had this happen to them? What did you do to fix it?
Thanks

[yhandor]

Could be the fuel pump. When I had my 2.2, I was crusiing, and it cut out, kept doing it, and then just died and wouldn't start, it was the fuel pump.