I need to go charge phone then I'll post some pics. I hate being critical, especially when he's the guy that's invested in his qualifications, not me. But I know I could truly have done a better job and have done pre gas safe days. Trapped condensate pipework etc.... Doesn't inspire confidence in employing 'skilled' supposed craftsmen.Well many of us do, do the gas safe registration from home as it’s usually the last job and you don’t have to be stood in the customers house to do it. The benchmark as far as I’m concerned is key. It should be completed to show the correct commissioning procedure. So he didn’t use a flue gas analyser?? Burner shouldn’t really need adjusting out of the box but should be checked. To be honest it’s not a case of getting the engineer in trouble. If he’s qualified he should know what he should be doing and not cut corners. Being gas safe is sadly no guarantee of workmanship. I always show customers pics of my installs or am happy to provide previous customers details for reference. The pipe runs could be down to a lack of communication. If you don’t specify then it is down to engineers best judgement. Show us some pics