the MkIII is more of a cruiser/touring car than anything, they are hard on ball joints and most of the suspension. the 7MGT-E is known for popping head gaskets. o ring and metal headgasket is recommended approach to remedy the situation. the CT26 is good up to about 14 psi, yes, and then it's out of its efficiency range. there is an upgrade (actually 2 well-known ones) for that CT26. one is a T4 wheel upgrade. it's pretty common.