2.5 or 3.0 exhaust

i would have built a 3" system but thats mainly since i like to have alitle space to grow,
i think that 2½" will be just at the edge of being enough for the level you are at, i dont think it will be a big loss in power, nice thing about keeping pipesize down is that the car wont be louder than necesary, 3" on a highcompresion,big cam 340 has a habbit of getting alitle loud.
for all out power 3"
if you want a car that is alitle easier on your neighbours ears and that will be alitle more stealty and can live with the possbillity of a small loss in power go for 2½"
since you already have the 2½" kit i would use it