P.P.E./I.S.P. Loss from Cybernetics and Bionics
  As most players of Rifts know, your mage or psychic does NOT want to get bionics. The main book says that this is due to the fact that mechanical augementation to the human body causes P.P.E. and I.S.P. loss. Even if the mage is missing both arms, has one leg, and is at -10 hit points, he would rather live as a cripple than suffer a drop in his magical ability.
  The explanation for this is a simple one. Psychics and mages use their bodies basically as energy conduits in order to work their powers. This is done by storing and chanelling  psychic energy through the nervous system and out of the body. Unfortunately, when bionics or cybernetics are added to the body they mess up the nervous system, causing a lot of mystic storage capacity to be lost, as well as affecting the ability to use magic and psionics.
 The Coalition has been known to use this to punish magic-users. They will capture a mage or powerful psychic, and force the individual to undergo full conversion, thus robbing them of the ability to use their powers. Bionics are known to cause a massive disruption of the nervous system. Cybernetics disrupt the nervous system, too, but to a lesser extent than bionics. This results in the fact that cybernetics cost their users less P.P.E. and I.S.P. than bionics do.That being the case, the following rules affect augmentation: 
 
*Bio-systems and cloned parts which are added to the body do NOT affect the levels of P.P.E. and I.S.P. of the owner.

*Reinforcing different parts of the body is done to help prevent the strength and stress put on the limb so that it doesn't rip out of it's socket. Each area which is reinforced subtracts an additional 1% x the number of reinforced parts. The areas which can be reinforced are the collarbone, shoulders, pelvis, spinal cord, arms, and legs.

*Partial Bionic Conversion: Partial bionic conversion replaces the arms and legs with bionic limbs, as well as reinforcing the collarbone, spinal chord, ribcage, and pelvis. Partial conversion reduces the recipient's I.S.P. and P.P.E. by 50% and also cuts the range and duration of psionics or magic by ½.

 *Effects of Full Conversion: Full bionic conversion replces the character's entire body, except for the brain, tongue, and often the original face. Those who undergo full conversion lose all but 1D4 P.P.E. and I.S.P., all spells, all psionics, as well as special abilities(ie, a mystic undergoing full conversion loses the Sense Supernatural Evil ability).
 The table which follows shows an approximate percentage of the borg's P.P.E. and I.S.P. lost to bionic conversion. This is represented by a % of energy lost(ie, R. Arm: -10%). This applies to both the borg's P.P.E. and I.S.P., not either/or.
Note that the number of slots indicated  in the brain entry refer to the number of implants which can be put in the brain.

PPE and ISP Lost to Bionics:
1. Head(total: -20%)
Brain(4 slots)-2% each   
Skull: -2%
Throat/Larynx: -2%
Eyes (2): -3% each
Ears(2): -1% each

2. Arms(2)(total: -10% each)
Hands(2): -3% each
Forearms(2): -4% each
Upper Arms(2): -3% each

3. Legs(2)(total: -10% each)
Feet(2): -3% each
Forelegs(2): -4% each
Upper Legs(2): -3% each

4.. Main Body/Torso(total: -40%)
Collarbone: -2%
Shoulders(2): -1% each
Ribcage: -6%
Spinal Cord: 15%
Pelvic Bone: -2%
Heart: -6%
Lungs(2): 3% each
Liver: -2%
Kidneys: -1%
Miscellaneous Internal Organs: -1%

PPE and ISP loss to Cybernetics 
1. Head(total: -15%)
Brain(4 slots): -1% each
Skull: -3%
Throat/Larynx: -2%
Eyes(2): -2% each
Ears(2): -1% each

2. Arms(2)(total: -5% each)
Hands(2): -1%
Forearms(2): -2%
Upper Arms(2): -2% each

3. Legs(2)(total: -5% each)
Feet(2): -1% each
Forelegs(2): -2% each
Upper Legs(2): -2% each

4. Main Body/Torso(total: -30%)
Collar Bone: -2%
Shoulders(2): -1% each
Ribcage: -4%
Spinal Cord: -12%
Pelvic Bone: -1%
Heart: -3%
Lungs(2): -2%each
Liver: -1%
Kidneys: -1%
Miscellaneous Internal Organs: -0%

After you finish figuring out what parts were taken and you have the total percentage of P.P.E. and I.S.P. loss, then figure out how much P.P.E. and I.S.P. the character has lost. Round down in case of odd numbers.

 Example One: Bob has 22 P.P.E. and is getting a cybernetic arm and a cyber-eye. This ends up being a loss of  7% of  his P.P.E., which leaves Bob with 21 P.P.E.  Two weeks later, some cyber-snatchers got Bob's arm… and he had to sell his sister's kid to get a new arm. 

Example Two: Nigel the Mind Melter is captured by the CS and turned into a partial conversion slave borg. The maniacal doctor replaces much of  Nigel's body, resulting in a 54% P.P.E. and I.S.P. loss, as well as another -6% P.P.E. and I.S.P. lost due to bionic reinforcement. Nigel's I.S.P. is normally 122, and his normal P.P.E. is 5. Putting this into the calculator, after Nigel's operation, he will have 49 I.S.P., and  2 P.P.E. 
 M.O.M. Implants, CS PSI-Implants, Psynetics, Juicer Conversion, and Bio- Wizardry don't cause P.P.E. and I.S.P. losses because  these devices don't really interfere with the nervous system of  their user as badly as bionics and cybernetics.