rx8 dies when let off gas

Ok so I bought a 04 rx8 with a132000 miles it had a it idled fine then would idle rough for a couple seconds about a month after I got it my gf shut it off after about 30sec...it flooded we pull started it got it to start but it burned up the catalytic converter. Needless to say it flooded I changed out the cat with a bhr midpipe I put new spark plugs and new plugs wires in it went to start it it wasn't turning over right so pull started it again got it running ran fine at high rpms. But died once I let of the gas and when driving it had no power and my check engine light was on before it started but currently is not...any ideas? Please tell me it's not the engine