It’s the torch itself, I bought a cheap one for starting charcoal chimneys, it does the exact same thing. My turbo torch that is almost 30 years old does not. I lay the bottle horizontal on it all the time lighting the charcoal chimney, zero issues.
Mapp will work on any torch that works correctly, mapp does use a little more air, (you might not get all the available BTU out of the more expensive gas) but will still work none the less.
This will be the last torch you ever buy….https://www.supplyhouse.com/Turbo-T...VWNpEOfeQzlaHm7RUPtWZkMw7LVxiRQ447jwTgfMJYWV0
On my weber grill, I've done the same, not sure if its the same problem though.... Then I read that the grill has a safety feature. If you have any of the burners turned to "on" when (before) you turn the gas bottle valve on, it senses that there is a leak and will not run at full speed. Make sure the burners are off, open bottle valve, then turn on a burner and ignite. After realizing the grill had this safety feature, I haven't had any more issues...
mapp has not been produced since 2008 in North America, it was a trademarked name to linde. Now it is propylene/propene
It's a good thing to have. If say for instance a turkey frier fire melts through the hose it won't start violently spraying propane everywhere.
I have a cheapo expert grill or whatever from Walmart and sometimes with a new bottle I get a low flow situation. Unhooking and rehooking it up fixes that as well.