How did you do max stats? Can you do that in the original Paper Mario (for N64)? Can you do max stats in Super Mario RPG?
No, unfortunately not. There are only 2 Mario RPGs that you can get max stats in by alternate means: Mario and Luigi Superstar Saga and Super Paper Mario.
In Mario and Luigi Superstar Saga, you must collect beans that you then blend together to create drinks at the Starbeans Cafe. Each blend increases a certain amount in a certain stat, but I personally used Teeheespressos, which increase a random stat by 6. By using many of these, you can result in obtaining 999 or more (max 1004 by using a Teeheespresso at 998 in a stat. It changes if you equip something.) in every stat for both Mario and Luigi. Unfortunately, this is very time consuming.
In Super Paper Mario, you must buy HP Plus or Power Plus items (formerly badges). An HP Plus item permanently increases your HP by 5, and a Power Plus item permanently increases your attack by 1. Both of these cost 2,500 Flipside Tokens each at the Flipside Arcade. Flipside Tokens can be obtained by playing games at the Flipside Arcade or buying them with coins. If you choose to buy them with coins (which is faster), you can choose to buy 1 token for 3 coins, 5 tokens for 15 coins, 10 tokens for 30 coins, or 50 tokens for 150 coins. By buying and using many of these items, you can result in obtaining 999 HP and 99 (Mario, Peach, Luigi)/198 (Bowser) attack. Similar to Mario and Luigi Superstar Saga, this is also very time consuming, except it's much more time consuming.
There has to be a limit to TTYD's stats, but I've never hit any of them before.
The limit is 200 HP, 200 FP, and 99 BP.