You can't just "get rid of" the catalytic converter. It doesn't matter that there are no formal inspections for it. It's still a federal crime to remove a catalytic converter from a vehicle, and not replace it. The clouds of dark exhaust smoke from a vehicle without a converter are pretty noticable, not to mention the foul exhaust stench. Either of those are more than enough for a law enforcement officer to pull you over and inspect the vehicle. You are looking at a $25,000 fine, and/or 5 years in prison, all to save $100-200.
If THAT isn't enough, people can DIE or get very, very sick from the carbon monoxide that an un-converted exhaust puts out. People have died from inhaling the fumes from rusted pipes ahead of the converter, and that was just small holes. Driving a vehicle with no converter is basically just being a jerk and not caring about your own health, or the health of others. People have the right to breathe air that isn't going to get them sick or kill them just because someone is too cheap to buy a converter or believes the false information that removing the converter from a vehicle will let it make more power or somehow run better. Both of those are untrue in the extreme. Modern vehicles are designed to run best and most efficiently with working emissions systems.
As for the converter, any of the replacements from Walker, Magnaflow, or other major exhaust companies should be fine. I doubt that the Magnaflow unit flows more than the other OE replacements, just aftermarket units sometimes flow more than the older factory units so they tout theirs as "high flow". The Walker kit supposedly is a bolt-on, though they now offer the converter hanger bracket as a part with a U-clamp, so my guess would be you have to either use that or weld on the hanger. The Magnaflow kit should be similar, bolt-on except for the hanger on the converter.
If you don't want to spend the $200-300 on a 2-converter OE-type bolt-on unit, you can get a single 3-way high-flow converter for well under $100, and have a pipe made up so it fits in place of the factory unit. I would suggest using a 2.5 inch converter and 2.5 inch pipe, which is the size of the factory converter. The pipe can be ovalized on the Y-pipe end and the factory flange either cut off and re-used, or some exhaust shops may have or can order replacement flanges. The other end is easy enough to just weld on a standard 2-hole flange with a little of the pipe sticking out the end, and use the same gasket as the factory, letting you use the same off-the shelf replacement parts as if it were a factory converter, if the positioning is still the same.
You can buy a cheap MAF adapter and cone filter, but I suggest going for the KKM kit, that has a machined aluminum adapter and S&B filter. The S&B flows more than the cheapo filters, and the high quality of the kit makes it worth it. I think it's also worth supporting a vendor that still makes products for the 1st gen Explorer.
You don't gain much if anything replacing the intake tube, but some have done it since the factory plastic tube eventually gets cracks and holes in it, and is $100+ to replace.
Overall, even on a bone stock Explorer, just replacing the factory air box with the KKM intake kit and replacing the muffler/exhaust with a cat-back like the Dynomax Super Turbo kit will be the biggest bang for the buck in terms of performance.
A new converter can also help, especially if the factory converter is in poor shape. Even a budget 3-way converter put in it's place should flow more and work better, just based on age and the advances in manufacturing and tech over the past 20+ years.
