Fast Printing first 4 layers only?

I have a Prusa i3 and am using Marlin FW with Slic3r. I'm trying to improve printing speeds now I have the quality where I want it and am having some success. But my problem is that the print goes really well (fast and high quality) for the first 4 layers and then slows down for the subsequent perimeters and layers. It then speeds up again for a single solid layer at 25 where I have a solid layer set at 25 in Slic3e, then goes back to slow again for the remaining layers. The top solid layer is also fast.
Marlin settings:
Default Max Acceleration (1000,1000,10,220)
Default Acceleration 1000
Default Retract Acceleration 1000
Ive tried to set Accel settings in Slic3r Acceleration control but for some reason the file will not save and Repetier Host cannot use the slic3r file, so I've left all the Slic3r accel settings at 0 which means ignore.
So, why does my print go fast for only the solid layers?

Check the speed settings in Slic3r / Print Settings. You can set different speeds for perimeters, infill, top solid infill, etc. I'm betting your perimeter speeds are much lower than your solid infill speeds.

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Nope, perimeter speeds are high (100) like all the rest.
Found out what the problem was though, there's a setting in Slic3r in Filament settings in the Cooling section at the bottom where you can select to "slow down the layer print time if below XX seconds" Mine was set to 20 seconds and this was too high for the layers that had infill because they would have printed faster than 20 secs, so Slic3r slowed those layers down. The solid layers took just over 20 secs to print so they stayed at full speed.
I set this value to 10 seconds and now all layers print nice and fast with perimeters and infill set at 100 mm/s and quality is good too! :-)

Solved, see my post above