This is coming from someone who runs a P5XLT on a regular basis.

P5XLT; C6TGC plug; Byrons fuel; 41021 manifold; 2084 pipe; on a Losi 2.0-T

Will go 10+mins runtime on *most* tracks and has been as high as 14mins.

It's close enough to the +4 mileage wise to come down to driver error.

For buggy...I'd stick with the 4. In truggy; without a doubt I'd pick the 5 everytime. Much more bottom/mid and doesn't give anything up on the top.

The 5 works real well on buggy too and will get mileage numbers. You just have to be a little smoother with your throttle finger

There's no great advancement in technology with the +4. It's a just a calmer engine overall.

Though the P5XLT now has a black crankcase, the castings are different.

The carbs, rear bearing *size*, conrod and other misc. hardware is shared.

However, the crankcase, piston/sleeve and crankshafts are different between the 5 and 4Team.

Personal choice, but for buggy the 4 is hard to beat.

Buggy: +4C-Team, 9901, 41021

Truggy: P5XLT, 2084, 41021

Since you're already running the P5 in a buggy, you'd probably be a little disappointed if you swapped to a 4 now. It's smoother, but also a lot calmer in the mid/bottom ranges where the 5 comes on like a torque monster.