Range Rover P38 2.5dse 1999 Diesel (psi Powerbox Chip)

Im Thinking Of Puting A Psi Power Box Chip Into My Range Rover 2.5dse P38 Diesel 1999. I Was Just Thinking, The Chip Wouldnt Blow The Head Would It? The Range Rover Has 93,000 miles On It. Are They Any Downsides To This Chip. Also Does Any1 Know Where I Can Get 1 of these chips In Leeds, Or By Leeds. For A Reasonable Price. Thanks