As far as food goes, I agree with Larry, Jill, Carl and the others: dry food in itself shouldn't be a cause of diabetes (just like eating carbs doesn't cause it in people, unless you're already genetically wired to be diabetic), but the extra carbohydrates that most dry foods contain
will require more insulin to be used for energy, and if it doesn't get used, you wind up with higher blood sugar levels. So you have to give more insulin to deal with it. Or produce more insulin if your pancreas is working, and in a diabetic cat with a pancreas that isn't quite fully functional, that could easily be the stress that causes the disease to manifest.
On another note from your post...
Yeah the BCP PZI insulin isn't dropping my overweight cats insulin either. I should have gone with Lantus but I went with this one since it was a cat insulin and not a human.
I'm not a doctor or a vet or a geneticist, so take this as you will, but from my experience at the human end of diabetes, I wouldn't put too much emphasis on "species-specific" insulin working any better for regulation. It's certainly worth trying to see if it makes a difference, but I wouldn't expect it to make that much difference: Human diabetics used solely beef and pork or pure pork insulin for decades before they came out with human insulin and the synthetic human insulins. Other than being more prone to getting "bumps and dips" at over-used injection sites (which seems to become a non-issue with the human insulins - admittedly because it is a species specific insulin for us), there was no problem for most diabetic humans staying at least reasonably regulated on these non-human insulins. As far as I could tell, what improved control over the years was developing very fast acting insulins (to use as a bolus for meals) and very long acting insulins like Lantus, so that we could keep a more continuous supply in the body. I was on a human-sourced insulin for many years (after several years of beef and pork insulins with the same duration of activity) before I was switched to super-fast and super-long duration insulins, and that's when my control improved - not with the switch to species-specific insulins. At that time, I remember that there were more than a few diabetic people who complained that they had done better on the beef and pork!
So give the PZI a chance (I have no idea how long to recommend waiting for a result - someone else with more experience with that insulin might be able to give you a more realistic window of when you ought to start seeing an improvement if it's going to happen), but if it doesn't work, you might want to consider trying another insulin with a different duration. It seems that different insulins work better for different cats, so you just have to find the best one for Pooper. And that might take some experimenting, unfortunately.