engine "sputtering" problem

ok...I have a 98gt...just replaced the fuel rail with one from a 97 (so I could change the regulator...can't do it on a 98)...I also added a c & l plenum...now it seems that my engine is sputtering...not all the time...just when I hammer it or sometimes at about 3/4 throttle...it FEELS like when a spark plug isn't working...or something along that line...like a cylinder isn't firing the correct way...

any thoughts?

thank you!

Spreadman said:

Could have a bad injector, or water in your gas. My car does the same thing when I get a bad tank of gas. I say run through that tank and then fill up at a reputable station and see what happens.

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hmmm..maybe bad injector...I actually just refilled last night, hoping that was the problem...I checked all the connections for the spark plug wires...all tight...may be a bad plug...thanks for the help..