Lurching at 60mph+ '95 Regal Custom 3.8
 

Hello!

I'm helping my girlfriend's best friend with her 1995 Buick Regal Custom 3.8. The vehicle has begun lurching at 60mph, especially before the engine temperature has reached half way up the gauge.

-CEL is off.

-I recently replaced the coolant level sensor when the light began flashing non-stop regardless of the coolant level, however it now just shines constantly w/o flashing, though no leak or other related issue can be noted as the coolant system remains under pressure and circulating.

-Serpentine belt was replaced ~1000 miles ago after it began tearing itself to shreds

-Fuel pump was replaced in 2013

I'm thinking catalytic converter but without a MIL/CEL I would really appreciate any second/third opinions. Thank you very much for your time and assistance.