Attach a shop vac with a looong hose ( at least two lenghts ) to your exhuast pipe, remove both O2 sensors from catalytic cleaner Install a bolt in the lower o2 port (after the cat) turn on the shop vac , keeping as far away from the truck as possible, spray a healthy dose of carb cleaner into the upper O2 port using short bursts, 1 or 2 seconds, waite 5 seconds, repeat untill you have used about 1/2 of the can of carb cleaner, allow shop vac to run for at least 5 minutes to clear the vapors out , re-install O2 sensors and wallah!! a cleaner cat with no welding, NOTE; Do this outside NOT in your garage, and keep a fire extinguisher handy , this project has the potential to go very bad very fast,