Kitbag is 100% correct in that the 106 only gave a modest increase in thrust (5% - up to the amazing figure of 5514lbf dry and 8245lbf reheated
) and that this in itself was a fortunate byproduct of an attempt to increase overall reliability and improve specific fuel consumption.
The 106 used proven components from 3 existing Adour engines, namely the Mk871 fitted to the Goshawk (Engine core) the Mk811 fitted to the Jag International (Reheat system) and the existing Mk104 (Accessories, filter packs, gearboxes)..... Unfortunately, good ideas like this rarely work out trouble free in practise, and the 106 brought with it its own problems.
The 106 suffered badly from rear end burnouts and shedding of the turbines. There were several potentially catastrophic instances of this burnout occurring, with one failure exiting the engine casing and missing the F4 fuel tanks above the engines by mm. Several different attempts at curing this were tried by RR, including a heat resistant spray coating applied to the insides of the jet pipes, 'anvils' being attached to the reheat spray rings and vapour gutters to prevent unburnt fuel build up, and several others. Unfortunately none of these completely cured the problem, and the issues dogged the Jaguar until its exit from service, with all engine issues being directed immediately to RR for investigation.
As far as maintainability of the 106's goes, this was much improved with the introduction of a digital control system, and the DECATS facility. However, losing the ability to make any flight line adjustments of the Fuel Control units, was a bit of a PITA.
Hope that answers a few questions for you.
Flipflopman