rattleing noise

When I take off as soon as the rpms reach 1500 or when I'm just driving at 1500 rpms I hear a rattleing noise coming from the front of the car... my friend had the same problem with his SVX and he brought it in and they said the bolts had rusted off so they welded his heatshield back on do you think that I have the same problem that he did or could it be something else, I have no exhaust Mods whatsoever....