Plumbing Questions? Ask a Plumber and Get Answers ASAP.
Unfortunately the answer to your question is no. Tankless heaters use a lot more gas (but in a shorter period of time) than tank type heaters. So they need larger capacity gas piping. That's one of the down sides that's seldom mentioned before folks purchase a tankless. There are other downsides to: ***** ***** /repair costs, quirky response to low flow situations to name a couple. When ALL costs are considered tankless heaters are no more cost effective than tank type heaters.
91k is still almost 3 times the input of a typical tank type heater so it would still probably require new piping. Also keep in mind the brand doesn't matter in this regard. If the tankless has a lower input it will have a lower hot water output. The one you mention is not likely to make for a happy user.