Land Rover Repair: P38 engine knock, exhaust downpipe, crankshaft sensor

Question
My 98 Range Rover has a knocking in the engine that escalates with the throttle.  
Just spent $700 on a tune up and they said that they couldn't tell me why.  Do
you have any ideas for me?

Answer
Hi Matt,

knocking sounds can be caused by many things:

catalytic convertor failure;
reluctor ring teeth not positioned properly and hitting the crankshaft sensor;
the rockers;
a mushroomed lifter and worn cam lobe (flat spot);
slipped cylinder lining (spells doom for the engine!)$$$;
loose exhaust downpipe.

Hope this helps,

JohnMc