My 2002 XKR coupe is in fine, stock shape after many replacement parts. Now that I am used to the car, I am ready for more torque from 0-40 mph. Rear axle change? Lower pulley change? Save the $ and go for AVOS twin screw setup?

Some members have new rear axles along with limited slip differentials. The rear axle sounds like it makes a major impression all by itself.

As I understand from various discussions re the 4.0 litre engine, the lower pulley upgrade provides more power down low and while the part is more expensive than the upper pulley, you spend far less time in labor. I will be paying a mechanic to do this.

I spoke with a mechanic who performed major supercharger work on a 2008 XKR with the 4.2 litre engine and he spoke of doing the upper and lower pulley on my car. Does that make sense?

Also, while I would like to have a more aggressive engine/exhaust sound, I'm under the impression most exhaust upgrades provide net power gain only at the top end while diminishing initial acceleration. Not acceptable as most of my driving is in the city and 0-40 MPH acceleration is what I seek most.

 

First off, Michelin's are not what you want on the car if you are looking for a good hookup.
If you go rearend gear change and you want to go over 3.50 ratio, you will need to beef up the rearend, i.e. HD u-joints, etc.. because lauching a 4k+ pound car is going to be hell on the rearend.

If you are looking for a stop light warrior, I would go gears and if you want to live in both worlds (speed and quickness), go twin screw SC, cam and headers.