97 Buick Lesabre 3.8 surges on acceleration

Aprox. 100,000 miles... just changed plugs (ngk platinums) air filter and fuel filter... The car's fuel milage was deteriating and aircare readings had worsed by 50%.

All were in need of change and now the car surges and bucks under acceleration at highway speed after it warms up.

Any suggestions? Is it possible the fuel lines being opened need to be purged?

Thanks

Martin