thundermustard

I have a one year old Trek 1200 with upgraded wheel set and new cassette on rear.
When I pedal with much power, I get a metallic tink type sound at the bottom of the left pedals rotation. It does not make it in the stand, while coasting downhill or on a level, easy surface. It makes it in the saddle or out.
I took it to my dealer and without really looking at it, they recommend I grease the threads on the bottom bracket. So I took of the crankset and greased the two male ends sticking out of the bottom bracket. I did not remove the bracket. The bottom brackets spins freely and smoothly.
I spoke with them on the phone and asked if that is what they meant and they said yes. They also said sometimes it is the headset even though it sounds like it is coming from the bottom bracket.
I took the bike apart last fall at bike school and the headset bearings were in bad shape.
I also put on the original wheel and cassette. It still makes the sound.
Any ideas on what I should look to replace. I am thinking do the headset since the bearings are bad anyway and then the bottom bracket.
I like to order from Performance Bike and how would I order the right parts. I have Tiagra components and a triple crankset.