Engine sputter???? Need help please

I have a 99 P71 and i am trying to work the bugs out. Its giving me a little bit of a shutter at low speed. When i get on it it seems to not have its full potential like somethings holding it back. When i bought the car it had a miss in cylinders 1 and 3. so i replaced the plugs and worked great. the car ran great for about a month then it started the problem chugging and kinda running rough. I just got my car outta the shop today i had the cats removed and straight piped it. I've been lookin up every thing i can off the net some say the EGR valve and others say oxygen sensors. I have not got a computer to read the codes yet. Any one got any ideas? Any info would be helpful thanks.

If you have an Auto Zone near you, they do pull the codes for free.

A decent code reader only cost about $50, and a good code scanner costs about $130. I use Actron Scanners. With all the new cars needing a code reader to find out what the problem is, it makes sense to go out and buy one.javascript:emoticon('');

Also, you may want to get you a copy of the Haynes Techbook on ODB II troubleshooting (p/n 10206). It does help some. But investment in the car also means investment in tools. That is unless you prefer someone else to fix your car.javascript:emoticon('');

Ok i found out that its my oxygen sensors before and after my cats (that arnt there) the guy there said i can have the computer reprogrammed or go back to cats and new sensors. Any one got a Computer reprogrammer in or near PA.??