1. A "FLASHING" SES light means the engine is running so bad that the catalyst is in danger. You may have removed the cats, but it's telling you something is VERY wrong.
2. Connect a REAL scan tool. Look at codes AND the data stream.
3. When using a piece-of-crap "code reader" or bottom-feeder scan tool, the P0300 is probably not the REAL code. A higher-quality tool would likely tell you the true code--a specific cylinder that's misfiring.
I dealt with this not two weeks ago. My own Trailblazer started surging during a gas stop. Stalled. Re-started, ran rough. I was away from home, so I pull into an Advance Auto Parts store. Counterman connects their junk code reader and proclaims "P0300, random misfire". If he'd have told me which cylinder was misfiring, I'd have bought a coil and installed it--but since his tool couldn't narrow down which cylinder was faulty, I drove home and connected my scan tool. Mine gave the TRUE code--P0301. I replaced the #1 coil, and it runs great again.
Running rich enough to set a code? Leaking injector? Have you replaced the terrible "Spider" injection system? What is the fuel pressure?