Owner of two 1996 4Runner's here. One I purchased BRAND NEW off the dealer lot, the other I purchased a few months ago from the original owner. Both are SR5. My used 4Runner had a harder life than the other one and has more miles. The ABS in the one I bought new works as well as when it was new, giving no trouble no matter the road surface. The used 1996 acts way different, often triggering over the simplest things. I haven't gotten it checked out, but I'm blaming this on time and wear, not Toyota. Both run different tires(Both run P-rated H/T tires with 90%+ tread, different brands) and brake pad setups(the one with good ABS uses recently installed OEM brake components, while the used one is running some moderately worn aftermarket components based on visual inspection), but I doubt this is the case either. I'll report back once I get the system inspected on the used one, but it still serves it's purpose for my driving conditions(some highway + stop and go traffic in the NYC areas).
Pull the ABS fuse at your own risk, but do not do it because same random dude online said it's an awesome idea. Then again, that could be a good lawsuit.