I'm a lil behind here, but my phone was acting slow too after I installed a few apps and then I removed them thinking that my phone was gonna go back to normal, but things did not go the way I spected it, infact it got slower, so this is what I did (of corse my phone was rooted running Froyo 2.2 T959UVKA7) so I whent in to cwm recovery and wipe the dalvik cache and the system cache* ---"do not erase the user data"
--- you'll lose everything unless you have a back up...GUESS WHAT HAPEN AFTER I DID THAT PROSEDURE? MY PHONE WAS FASTER THAN EVER, It took a min to start back up again but dont get desperate... SO IF YOUR DAD WANTS TO KEEP THE SAME ROM THIS MIGHT HELP YOU A LIL BIT and yes you can do this procedure on eclair too...
Sent from my SGH-T959 using XDA