Flashing yellow Engine management light on ford fiesta mk6 2002-2003

Flashing yellow Engine management light on ford fiesta mk6 2002-2003 Help?!

Added (1). ok so today my engine management light came on wilts i was driving slowly in town today
quite a hot day

the car feels as if it is struggling to accelerate after it warms up

i filled the water reservoir to the max yesterday

maybe i need to add coolant?

it gets rather hot under the bonnet even if i drive it for 5 minutes to work etc…

Added (2). it feels sluggish and struggles to get up speed

it sort of bumps… Jigs when i'm stationary… At lights etc…

What should i get Fiesta ST, Mazda 3 OR BRZ? And why?

Looking to purchase a new car!

Just to note: I HAVE driven all three of these cars (Plus many, many others)

I realize these cars are all very different but i have narrowed my search down to these three:

2015 Mazda 3 i sport - Affordable, Luxurious, Poor performance

2014 Subaru BRZ (because of financing options) - FUN, Quite the looker, Most expensive costs and insurance

2015 Ford Fiesta ST - Enjoyable, pretty fast, moderate price but it's a ford.

I really can't decide and would like to hear some input, I've never heard of a comparison of this nature.

(If I could wait for the new eco mustang i would. But i can't because my car was recently totalled and need transportation.)

Added (1). fiesta seems to be the consensus i guess