Vibration and wheel click

Hey,

Just got back from a weekend excursion, and while cruising along the highway I noticed a 'rough' vibration in the handling of my '04 V6 between 2500 and 3000 rpms, noticeable only in 3rd and 4th gears, but much more profoundly in 4th gear. Acceleration also seems to be restricted in this rpm range and shifting down to 4th from 5th to pass the Sunday drivers has become more of a challenge than a slight adrenaline rush. I assumed a wheel alignment issue may have been the culprit, but then I asked myself why I would be experiencing this loud roar and vibration in the engine bay at consistent RPMs, not speeds. Could a wheel misalignment still explain this activity? Or should I be concerned of a more serious problem. Also, I believe I could smell faint engine fumes when pushing the engine (i.e. when trying to maintain speed during uphill climbs), although this may have been the exhaust fumes of the hundreds of other cars on the highway.

Also, at very low speeds (1st and 2nd gears), I can hear a faint, fast, repetitive clicking in the engine bay, audible only to the trained ear, something I had not heard until today. In addition, I hear a distinct 'click' in what I believe is the front axle when I turn the wheel to the left only (while both moving and idling). Brake caliper issue?

I'm not sure if these problems are related or independent of one another, some of which may be my overactive imagination! Nevertheless, there is nothing worse than an unreliable 10-month old Mustang. Having already lost a 2000 mustang last summer, my conscious exaggerates every sound, smell, vibration, and sight that appears to be out of order with my '04. However, being slightly obsessive-convulsive with regards to cars can be of benefit......kind of like an early diagnosis of a treatable cancer in a way!

Anyway, if you have any suggestions, solutions, explanations, please let me know.

Thanks,

Just A Guy