Odd surge - any ideas.

[Mad Max]

I just got the Cobra back from the dealer. I mentioned the problem, but they were so slow fixing another problem, they must not have test drove the car.
Anyways, I have a 03 Cobra. Bought with 8500 miles. Mods (that I am aware of) consist with CAI and Bassini catback.
The problem is that while driving in 3rd or 4th gear at 35-45mph at a steady speed, the car surges and eases up - its almost like its getting fuel and then not - but no trouble lights come on and the car pulls like a beast with no hesitation with your foot in it.

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[Flatliner]

Check to see if your mass air meter and what o'clock it is at. Check for any leaks from the filter up to the throttle body... then get back to us. Do you floor it when this happens, little throttle, wide open?? Steady speed could mean a lot...

 

[Mad Max]

Have not looked yet, but it is at a steady speed.

 

[Juggernaut]

PLUGS!!!!, i get a surge at idle, at a light in traffic the R's drop to 250 and then bounce back up to 750-850...i cant explain it so i hope i just need a tune fixed

 

[Mad Max]

The surge thing comes and goes - very minor. What I am feeling is drivetrain slop - almost feels like worm universal joints?