93' 5.0 LX spark problem??

Ive got a 93' LX 5.0 automatic and just today i decided it was time to replace the spark plugs in it. Car was running perfectly fine before hand, i bought the exact same plugs that were in the car, gapped them properly, installed and now the car wont run worth anything. It revs up perfect, if you put the transmission into "1" instead of drive or overdrive it will take first gear out smoothly all the way to 6k rpm, but once its in drive or overdrive, the second it changes out of first you dont have any power, car wont downshift into another gear in WOT. Any suggestions??? Ive double checked all my plug wires and double checked the gapping on the plugs and still the same thing. Thanks

interesting issue: are you in california? I know that my 5.0 had its timing advanced and you must simply moving each plug wire one position counter clock wise. as i understand it this was done in conjunction with other modifications to clear California emissions. if you are using the schematic out of a chiltons or something you might not have it wired properly.

does it sound like it is miss firing?

It sounds like its firing just right. When i was replacing the plugs i did one plug at a time to make sure everything was exactly the same way it was before so i didnt put the wires back on properly. And like i said before when its in park u can rev the engine up perfectly, not sluggish or anything.

Is it throwing any trouble codes?

I havent tried anything with the codes because i dont know how personally. Ive had a friend tell me its a "speed sensor" or something along those lines and my transmission doesnt know when to shift being it goes into 4th gear at 25mph.