I know what you mean blowing through the budget. I'm using Areoquip PTFE hose for everything. It's good to 3,000 psi. So my hydro boost is getting it too.
The exhaust stud. I use 312 stainless electrode.
Here is one store
https://store.cyberweld.com/hobart-3...80630-rdp.html I bought mine locally.
The 312 in 3/32 size burns hot enough to stick and the flux protects the metal around the bolt. I've removed a lot of broken bolts and studs that are below the surface. I weld enough to stick to the bolt adding about dime or nickle in height. I would clean and stack another bead on top, repeat until it's sticking out enough to put a nut on it, then weld it with the MIG welder or 7018 rod.
Tip: place a washer over the stud before starting. This protects the metal and forces you to be dead accurate on your welding. I used foil tape because I had it. But it protected the aluminum head from splatter.
To test the theory the flux protects the metal around the bolt. Put a nut on a bolt so its recessed, weld to the bolt and repeat so the weld is above the nut. Then put the bolt into a vise and use a wrench to take the nut off.
This also helps you get practice before the real deal.