Hi there all, I am new at this and am doing this in the hope that someone can help me/us.

I have a Peugot 307SW Diesel, HDI 110. I am probably going to sound a bit selfish at first but I can promise this is not the case. I love my car and I love my dad. I returned a couple of days ago from a 2 week holiday to find that my 76 year old father had decided to give me a nice surprise and change the EGR valve on my car knowing that I had had problems with it for quite a while. He has always done the work on our cars but in recent years due to age has simply stuck to the occasional oil and filter change. It turns out he was told the EGR valve on my car was at the rear bottom part of the engine and that the engine had to be partly removed to access it,( this later turned out to be incorrect). To cut a long story short he has changed the valve but on reassembling the engine clearly something is not right, the engine sounds awful as if it is blowing or has a broken exust and when pressing the excelerator fully the rev counter doesn't even touch the 3000 mark. He is gutted as he feels he has made matters worse for me and I cannot afford to take her to a garage. He is determined to solve the problem but to try and help him can anyone please give me a guide line as to what the problem could be. He knows I need the car for work and feels he has let me down,,,,,,,,,,,,, please please please,,,,,, can anyone help !!!!