Injected "base" (amphetamine sulphate paste) many many times in my past. Just to counter a comment above it is a salt and cannot be smoked.
It is always cut with endless insoluble crap no matter the quality. This is setting you up for some serious complications if you miss a shot or even if you dont.
If you are determined to do it use a micron filter and do not heat the water, just dissolve what will dissolve and filter well
Personally I dont think the rush IV is worth it at all compared to something like IV cocaine, mephedrone or ethylphenidate. I was more just addicted to the needle rather than this being a particularly awesome ROA for amphetamine sulphate. Would recommend just drying and snorting it. 1000 times safer, not really any less intense