That's because JF17 engine is RD33 engine.This engine is often appear inadequate lean oxygen combustion phenomenon.So it looks dirty.
F16 and F15 engines don't need to waste gas.
What you said may be Saudi Arabia.J31 design problems on the engine.RD33 engine.Now Russia only to producer in China and Pakistan.Export machine is J31 also use even no.Resistance.
In your opinion F16 stronger than JF17 a lot?Certainly better than LCA right.
I am in shenyang.But shenyang aircraft company lack of funds.Countries now to do j-20 aircraft and bombers.No money.China is not so rich as to Pakistan.
J31 estimate becomes SU47 without capital.
But too much better than Japan's fourth generation machine.
Pakistan need most is a high-performance awacs and attack aircraft.
Nuclear submarines need supporting facilities is very large.And just attack submarine's words a little bit small.
The five nuclear powers in principle can't sell and transfer of strategic nuclear weapons.This is not the atomic bomb.Pakistan with China's diplomatic pressure.Unless India provocation.