How much faster will my car accelarate if i put sport exhaust system with 4-2-1 manifold and remap the engine?I own a peugeot 206cc 1.6 16v.?

Long story short - you might notice a little bit better acceleration and the car might feel a little quicker in a straight line, but it still won't feel like a "fast" car compared to many new cars available today.

Long story longer - Say your modifications add ~10% more power across the entire rev range (which is probably, at most, what those modifications would add in total). To simulate what the difference in acceleration would be before and after, you could have a heavy passenger (or two lighter passengers) who equal about 10% of your car's weight (in this case, about 265lbs/120kg) ride with you in the car before you modify it and accelerate from a 0 to ~60mph as hard as you can (full throttle). Then, have the passengers get out and do the same 0-60mph test at wide open throttle again - the difference in acceleration between when your car had passengers and when it had just you, the driver, will be about the same as if you added 10% more power through engine mods. Good luck.

You will, of course, be informing your insurance company about these modifications. If you do (of course I mean WHEN you do) your insurance will go through the roof. If you don't your insurance will be voided and you will be driving uninsured.

It will probably just go faster to the scrap yard at that age.

it will not go as fast as your insurance companies rejection of your policy unless you inform them ...then your insurance will go through the roof ...but if they do reject you your insurance with another company ..if you can find one ..will go into space!!...with no cat the car is not roadworthy either...instant fail the mot

No one can answer your question simply because an exhaust manifold only works in your favour IF it is designed correctly ( and you don't mention which company's manifold you're installing ) and also no one knows what will be changed if the computer is remapped.

I forgot to mention that the exhaust wont have a catalytic converter, and it has 110hp and 142nm torque stock