I had the exact same problem with NFS:MW and had made a thread about it a while ago.
Turning down the graphics settings never helped.
EDIT: here is the link to that thread
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However, I found out that my problem was related to heat. Wierd I know, considering that none of the other games behaved that way, and I dont o/c my system.
When the ambient temps were > 30 deg Celsius, (my room is non a/c) the game would stutter every 20-30 seconds, unfailingly. However, when it was cooler in the night, or raining outside, and temps were < aprrox 26-29 deg C, it would run smoothly.
I am currently running it at 1280x1024, 4xaa/8xaf, medium world detail, visual treatment low (reduces the ugly bloom), shadows off and all car details maxed. I get between 35-70 fps depending on the map area, with City being smoothest and Camden/Refinery the lowest.
I do think that the coding is inefficient. The graphical effects are not so great that a 7800gt would have to struggle through this game.