iMac mid 2011 slow boot

I bought a second hand iMac mid-2011 in 2014 summer with ML 10.8.5 in it, and without doing a fresh install, upgraded to Mavericks. My system in fully upgraded, to 10.9.4 and it's boot time is like 3mins while my 2006 mac mini starts up in 35 secs. I am really frustrated. I found a script, and added it to my startup items. the login (Which takes bout 2mins) was faster, but the boot time is them same. the script is:

roperty systemList : {¬

"com.apple.ATS.System.fcache", ¬

"com.apple.ATSServer.FODB_System", ¬

"fontTablesAnnex"}

property localList : {¬

"501:Classic.fcache", ¬

"501:Local.fcache", ¬

"User.fcache", ¬

"Classic.fodb", ¬

"Local.fodb", ¬

"User.fodb", ¬

"FondResourceCache"}

tell application "Finder"

set versionFinder to version as text

end tell

if versionFinder starts with "10.3" then

set localCaches to ((path to "cusr") as text) & "Library:Caches:com.apple.ATS:"

set systemCaches to ((path to "boot") as text) & "System:Library:Caches:"

tell application "Finder"

repeat with name in localList

try

delete file (localCaches & name)

end try

end repeat

repeat with name in systemList

try

deletefile (systemCaches & name)

end try

end repeat

end tell

end if

Please help me. I bought this mac for around $1000. my specs are :

iMac 21.5 inch mid-2011 (base model)

2.5GHZ 2400S Core i5

4GB 1333 MHz DDR3 RAM

AMD Radeon HD 6750M with 512MB of VRAM

OS X 10.9.4 (13E28)