I have a dear friend that owns a 2000 Jag XKR. For 3 years he has an on and off P0171 and P0174. Clearly proper diagnostic procedure would have you start with vacuum or other air leaks, especially since when he is cruising at at speed be it 20, 30, 40 or 60mph his LT are at +19.5 and ST stay in that range up to the +25. However he is one of these types that thinks he is a great mechanic and has 11 old cars sitting around that cannot start or be driven and of course has a "unique" problem. I am sure all of you know the type. My question is not about the codes be thrown . I understand how to deal with those and what the causes are. But he has decided that he is going to throw parts at it and replace the MAF. However he ordered and thinks it is going to work a MAF that is intended for an XK8 and not the XKR. I am curious that with putting an incorrect MAF on the car what you think the results will be or how the car will react? Thanks Tom in Dallas as a side note: My opinion from knowing Jags is that he does NOT have a MAF problem at all and he has thrown zero codes to indicate the MAF is out of range in any way.