went to pick up my car today, it had set for around 6 months before I got it to a shop to put a trans in. got half mile down the road SES light came on and it stumbled slowing down then struggled to idle when i pulled into a gas station. Got back to the shop and i think it had a p0442 code I think it was evap leak or surge somethin like that?

They thought possibly a stuck solenoid and pointed out the gas cap o ring was toast, all dry and cracked.

What you guys think? just looking for some reassurance that it's hopefully nothing after shelling out some money for a rpm transmission ha

The shop builds full blown race cars and built my friends car that never had an issue. the car was shifting fine on my way to the station so i do believe its just bad luck.

 

My first guess would be an EVAP purge line cracked while the trans was being done. This could cause a very lean idle condition if the solenoid is open, which could be in question after sitting for so long. BTW, respected high performance shops don't always check for emissions crap. It really isn't their thing.