That is the problem with any stimulant based preworkout supplement. They all say take on empty stomach for best results. I used to take Nano Vapor(till it gave me diarrhea) on full stomach and did notice that the pumps were less as compared to empty stomach. I increased the dose and got better results(pumps), till I got the runs. However, I think the complex carbs taken 1 hour and the fast acting protein(Whey) 30 minutes before workout are absolutely essential and should not be compromised on. Everything else is optional in my opinion.
My advice- Increase dose of the Animal pump(if possible) & eat as advised before the workout. This will yeild better results in the long run.