CrAkD X 95TA

ok we put in a new ASC water pump and hypertech 160 degree thermo....well we were in there we notice the ignition coil was corroded a little bit so we went down to GM and bought a new coil and installed it as well got it all back together and it wouldnt start at all so we figured wed try hooking up the old coil it fired up right away after hooking up the old coil so we were like ok the new coil is crap so we took the new one out and mounted the old one now it wont start again and it makes kind of like a sucking sound or backfire sound coming from the throttle body any ideas?