Why did you put the injector cleaner in in the first place?
Without knowing anything about the car, I'd say an injector is stuck open or something like that; fuel related.
It could very well be that the cleaner broke something loose that is preventing an injector from closing. That will dump too much fuel. It may be enough the puddle in the intake manifold. During the overlap period of the cams they need to breath back into the intake, if fuel is blocking the path it can backfire; the overlap air is warm.
If this is the case, pull the fuel pump fuse and try to clear any extra fuel this way. It isn't the safest method but so long at your careful it works.
Once the car dies on it's own, try starting it a few more times just to be sure.
Then pull the connectors on the injectors, put the fuel pump fuse back and try to start the car. If it starts or makes a better attempt than previously, odds are an injector is stuck.
My best advice here is the have a shop flush the lines and replace the fuel filter. Then replace all the injectors with known good ones.
13 years, 124,000 members and still no sponsored racing.