Myself I'd say gears. Everybody likes to do gears because it gives you a kick in the ass. In my experience, after the fun of burning out in 2nd wears off, you realize the car really isn't that much funner to drive, and the short gears become more of a pain in the ass. I had a Notch with 3.55's that did a best of 14.3 Later on a had a Vert with stock 3.08's that did 13.8 Neither car had much else done, I just felt like the 3.08 gears were better suited to the track length, like with the 3.55s the car started running out of steam while the Vert still pulled right up to the end. I've got another Notch now and plan to STAY with these 3.08's, love the long pulls through 2nd gear. Gears can cost a bit too, like up to a grand to have them done professionally. For that money I'd rather put it into an explorer head/intake upgrade. What other popular mods do you recommend to steer clear from, and why ?