+1 on the P-Rail. It's a more authentic P-90 tone than the Phat Cat is, let alone the Mean 90 which is significantly overwound. If getting 'the' P-90 tone is what you want, using a P-Rail and just wiring it only as a P-90 is going to get you there better than anything else.
That said, my personal favourite is the Irongear Alchemist 90, which is a lighter take on the Phat Cat formula. The neck model is only wound to 5.3k (+/- .1k), which is low even by P-90 standards. I actually use the bridge model in neck positions, since that's wound up to 7.5k; still lighter than a Phat Cat neck, but doesn't get drowned out by bridge humbuckers the way the neck Alchemist 90 does. If you go for either of them, just bear in mind Irongear's pickups are made with 'Fender phase', so they're inherently out-of-phase with Seymour Duncan pickups and most other manufacturers. To get them back in-phase with other pickups you need to switch the hot and ground wires of one of the two pickups, or physically flip the magnets over.
That said, the Mean 90 you have is specifically made to be extra-hot, so it's no surprise it's "booming", especially if you have it near the strings. That's a hot wind + double A5 magnets for you. You'll be able to get rid of some of the low-end just by lowering the pickup from the strings, so try that first before you go spending money on new pickups. In relation to that, any of the three pickups I've mentioned (P-Rail, Phat Cat, Alchemist 90) will be less bassy than the Mean 90.
