96 GT missing under load??

My 96 gt is missing under load say your going up a hill in 5th or under 2000rpm... misses bad! seems ok at upper rpms! tried new plugs.... same thing.. Almost sounds like a clicking under the hood plug wires???? they are MSD so i was hopping they are good but they were on the car when i bought it so i have no idea how old they are.. any ideas??? thanks

PS just got the pi intake swap done but it missed before that so i dont think its related... PLUS i bought the PI intake that doesent require RTV in the corners etc.. I had thought my cracked intake had somthing to do with the miss but guess not.

Replaced my 8.5mm msd wires with 8mm motorcrafts and it fixed it right up! BTW the pi intake swap was WELL worth it.... Alot more power and sounds meaner at the upper rpms too!