Weird Turbo like noise when accelerating

Hello

I am having 2 problems with my car and I cant really afford to fix every possibility so I was hoping someone could narrow it down for me. Firstly, my temperature gauge is always low, sometimes gets a tad higher when on the motorway, but usually it reads quote low. Ive heard this could be a thermostat stuck open problem. Is this correct?

Also, sometimes, when I am accelerating, the engine makes a blowing kind of sound like it has an air filter on it, or like the sound you'd expect from a leaking exhaust (But its coming from under the bonnet). This doesnt happen every day, and it doesnt happen once im out of first gear. (The car also lacks power when accelerating but im not sure this is part of the problem as it is only a 1 litre)Ive read quite a few possible problem areas, like the manifold, ICV etc etc but I could do with know what exactly it is if anyone knows. If anyone can help, Id be really grateful. The car is a vauxhall Corsa S reg 1999 1.0 3 cylinder.

Thanks in advance :-)