I have a 1992 Subaru Legacy GT turbo.

When the car has been sat overnight or for a few hours, i am having trouble starting it, it can often take at least 5 attempts and it seems to be getting worse, I have changed the battery and sparkplugs so its not that.

And if i pump the gas then that cuts it out all together, i can also hear a knocking noise, once the knocking noise goes the car then starts. I have to then wait a few minutes as the car can be a bit sluggish, so i have to wait for it to warm up before i drive off.

any advice would be appreciated
Cheers