To respond to your shop's comment. They're right, any set of new injectors from a reputable company will be pop-tested and adjusted, but you're not installing new injectors. You're installing new nozzles in your old injectors, if they've NEVER pop-tested injectors then they've never rebuilt a set, only installed new ones. The parts that actually effect pop pressure (The spring and shims) aren't being replaced in your case. If you only install the new nozzles without pop-testing your injectors you've only done half the job.