P2118 - Suzuki verona

Question

I'm having a re-occurring stalling problem, with occasional hard starting afterwards on our 2005 Suzuki Verona with 72,000 miles. I drove it 35 miles a day for 3 weeks without incident, and without fail the 1 day my wife drove it 10 miles the problem occurred again. Afterwards the engine would start and immediately stall again, taking 3 or 4 times to finally run again. I have noticed a fluctuation in engine power when holding a steady speed/load, and when the cruise control is in use. Code reader gave 1 error code; P2118. After clearing the code the engine started right up & now seems to be running properly again. We had a major engine low power problem 4 years ago, and the throttle body was replaced by the Suzuki dealer. Not sure I completely trust where we had it serviced the last time. My brother & I can usually take care of things like sensors, and timing belts, but I'm thinking this requires more expertise than we're capable of. Is there something that we should look for/try, is this something that I should have a good local shop troubleshoot, or will I need to return to the same dealer that used to sell Suzuki's?
Thanks in advance for any help, info, and guidance.