1 HVAC Heating problem & 1 ignition problem 99'XJ

Here is the first problem. My heater cuts out when the truck is under any type of load. It seems like it diverts the air to the defrost(not floor).What do you guys think?

My second problem is when I start my truck at anytime regardless of how long it has sat, will run great for about 3min then it seems like it retards the timing and runs super rough. You can hear the intake suckin mad air and the motor will just about die, but doesn't. After 3min of that it corrects it's self and runs like the best jeep ever made. It has done this since the day I bought it, stock, about 4 years ago. i have serviced my ignition system and it did nothing. Getting ready to upgrade ignition system to MSD offroad 6 and wanted to rectify this issue before proceeding. Any advice is greatly appreciated!!!!!!!!

You have a vacuum leak or disconnected vacuum lines going to your vacuum canister in your bumper, passenger side. Check it out, try and find any cracked lines etc. I had the same thing and it was a cracked hard line, fixed it, relocated the bottle, and wallah it works.

That's a good call! I have already had to put a repair patch on a piece of that line. Well it looks like I'm going to replace the entire line this time. Thanks for the info!!! It really makes trouble shooting easier...

could be a leak somewhere else too.