Need help with LS
 

My car ran fine until lastnight after a good 15 minute ride not getting on it or anything anyway im cruising and all of sudden it feels like it misfires (putters from exhaust and feels like you hit a bump) so i get to my location it it idles horribley surging from 700 rpm to 1,000 rpm sometimes dropping to 200rpm's and putters so i replaced the spark plug wires and spark plugs still does the same thing im thinking its the distributor what do you guys think?

it's not throwing any codes either