P300, P455, P128 Codes after head gasket replacement.

I guess it depends where they were set it might but they can runa pro cleaner through them that works a heck of a lot better than the intank stuff. It may not be the injectiors giving the problem anyhow with a misfire. All sensors have to be checked.128 is a coolant temp problem and 455 is evap large leak so there may be a line off or broken leading to canister take it back and have them fix it right

Don't know what to tell you on that but I understand.

I would think so unless it had them prior to teardown which it may have had the p300 code. But the others I'd check for a line off on the 455 code and the temp sensor cold have failed or they pinched a wire going to it. Check to see if temp sensor is plugged in and look by back of engine for lines off or pinched together. I still think they should correct the problems, I know I would not let it leave with those codes until I was sure what the problem was. Especially the 455 and 128 codes.

Not really a timing issue one of the sensors is misreading as well as any air leak like duct work and or grommets leaking. That would only be for the misfire code the other two are either a bad gas cap or a evap canister purge problem which really should be smoke tested to find the leak. I don't' know how much you can do but these clowns that worked on it should fix this. To eliminate engine problem do a compression test on the cylinders that aren't firing. It could be low on compression as well. If it were a timing issue like a timing chain all your compression would be very low like all cylinders. And I'm sure it's not that. The ect shold be checked for apoor connection but you need a scanner to erase the codes first to see what comes back anyhow. If you have access to a tech 2 or a balance tester for injectors you can find out if your injectors need replacing g or not. That would end the debate on that. Also if you have tech 2 you can close the evap solenoid and see if that is the problem.