What you are suggesting is indeed possible, but it is a novel's worth of explanation and would also require you to engage in a fair bit of command-line activity - presumably using ADB from a PC. (You can do the same stuff from a terminal emulator on the phone, but that is horrible, tedious work).

Not only that, but it would require you to either use a different ROM's boot image, or you would have to unpack the boot image that you currently have, modify it, re-pack it, and flash it to your boot partition. Either way, that is more than just a few tweaks here and there.

The basic method involved is not too complicated - but the devil is in the details:

- back up 100% of your SD card to your PC
- partition it using Amon_RA (set swap=0, and ext to something reasonable like 512M)
- restore the (fat32) SD contents to your card
- install a boot image that causes the ext2/3 partition on your card to be mounted at boot at some place like /system/sd.
- manually mount the ext2/3 partition on /system/sd, create a folder called app, copy everything out of /data/app to /system/sd/app
- remove the folder /data/app and replace it with a symlink that points from
/data/app -> /system/sd/app

That's only an outline. If you want detailed instructions of what goes on during the a2sd/app2sd setup process, download the relevant "setup" scripts from XDA and start reading them. If you are clever, you can probably push them to the phone and execute them - but that still won't relieve you from needing to flash the boot partition.

I don't know why you don't want to flash a new ROM; if it is the effort involved, then what I am suggesting above is way, way, WAY more effort than that.

Good luck; whatever you choose to do, make absolutely sure you have a good Nandroid backup first - and save it to your PC as a backup.

eu1

 

This may help: [Script][A2SD] Darktremor Apps2SD 2.7.5.3 Beta 02 (01/22/2011) - xda-developers

But, I agree with EU1: you are probably better off installing a ROM like xtrSENSE, which moves cache out of the data area and leaves tons more room for apps and data - meaning that apps2sd is not required - or PlainJane2, which is pretty stock but has apps2sd support built in.

I'd Nandroid backup what you have first, but I understand that you can go from stock, rooted ROM to xtrSENSE or PlainJane without a data wipe first, meaning that you may be able to keep all your apps, data, SMS, call logs, etc., without having to backup and restore first.