Possible lambada issues

[WNR26]

Hi guys fairly new too the forum, I've had my 07 197 for around 5-6months now after owning a artic corsa vxr and fiesta St / zetec s's I felt like a change too something with what I would say a awesome handling chassis for a small hatchback ! Besides all that I have the apparently common 3rd gear glitch which I'm not too bothered about but I've now developed a slight problem with what appears to be the emmission system on the car, was driving down the back roads couple weeks back went over a bump and the car then developed a loud rattle, no affect on performance so first conclusion was heat sheild, after further investigation turns out too be heats sheild has broken all the away round the retaining clip. Once I had got to my destination ( at this point no lights had come on !) I stopped switched off engine and did what I had planned to do, when I returned to the car later went through start up procedure and my engine mangement light has now appeared with check emissions being displayed above the dials, started her up no problems started too drive off again no problems got about 150yards down the road and the car began too hold back on me cutting revs right down too nothing dipped the clutch and gave it a Rev with no response. After about a 30 secs it cleared and car began revving as per usual drove home no issues just rattling still, now once I leave it over night first start up its fine once I stop and then start it up again the same produce happens but now for allot longer up to a minuet, my guessing is perhaps post O2 sensor is faulty reading massively high emissions and cutting fuel too engine? I've noticed the lambada plugs are not well protected underneath the 197's is this something anyone else has experienced ? Any help much appreciated Alex