Missing and stalling

: Hello, Im dealing with an ongoing problem. Recently I ran my tank low and my sub died at take off. It is a 89 chevy sub. 5.7 litre. Ive replaced the fuel filter and put a bottle of heet and injector cleaner in the tank that is now full. Ive had very bad miss firing and stumbling. No responsse from the accelerator at times. After putting the injector cleaner in it now starts fine the first time but after it idles down it will stall. I have driven it hoping that more of the injector cleaner will work through and clean out what ever is causing the problem. But I have to keep my foot on the pedal when it is in gear or it will die. The sub finally threw a error code today that was 43. I believe it is the electronic spark control circuit. It is also pinging very badly when I give it gas while in gear. Any thoughts. Brian