Newbie idle/surge
 

So, I'm new here and i hope someone can answer this question for me. I have a 7mge motor i swapped into a 4 runner after i rolled my previous pickup with the 7m in it. The motor has been sitting for a year. I transfered everything over and started it up finally and....

1. With just the headers on
The motor started and idled fine for a few seconds

2. I put the rest of the exhaust system on
The motor turns on but then almost dies/ surges very slowly. If i hold the revs up at all when i let off the gas the car stalls

3. Took off and unplugged the a/f meter and intake
The motor idles fine....

So which parts needs cleaning or replacing

The catalytic converter might be bad. That will make u lose A LOT of power.