MAJOR UPDATE
I found other 2 versions around the net. Both claimed to have Wifi support already and working on most flashcards. R4 users also had confirmed both versions to be working offline and online. One has slightly smaller size than the other. I personally tested version a and it works flawlessly along with Wifi but version b did not work in multiplayer aspect. But perhaps it will work on others. So I decided to post two versions for people who still cannot play the game at all.
I have yet to discover the differences between the two, perhaps this is about different fixes for different flashcards story again. Please post your results and findings so we can make a distinction between the two. Especially Ezflash IV and other brands. 
Anyway Firmware updates addressing GTA issues has been released gradually by manufacturers so try to update your flashcards and run clean unpatched rom
For those who would like to play this on PC, you can use this no$gba emulator and run it with unpatched rom as well.
Emulator
Megaupload
| Code: |
| http://www.megaupload.com/?d=GEN5J8QF |
Rapidshare
| Code: |
| http://rapidshare.com/files/212379377/no_gba_w.zip |
Here is the clean unpatched rom
Megaupload
| Code: |
| http://www.megaupload.com/?d=TAYK7KJT |
Rapidshare
| Code: |
| http://rapidshare.com/files/210249121/GTACW.rar |
WIFI SUPPORT
Version A
MEGAUPLOAD
| Code: |
| http://www.megaupload.com/?d=ETGXPV6R |
RAPIDSHARE
| Code: |
| http://rapidshare.com/files/210166064/GTACW_WIFI_.rar |
Working on:
-M3 Ds Real(Me)
-M3 Ds Simply(Me)
-R4(majority)
-NDSTT(alimami2)
-Ninjapass evolution x9(twotonewolfetone)
..and the list continues
Version B
MEGAUPLOAD
| Code: |
| http://www.megaupload.com/?d=UXG2DB8S |
RAPIDSHARE
| Code: |
| http://rapidshare.com/files/210167746/GTACW__b_.rar |
NON WIFI SUPPORT
For other flashcard users except CYCLODS & EDGE
Patched Rom version 1
MEGAUPLOAD
| Code: |
http://www.megaupload.com/?d=M27IMGEK
|
RAPIDSHARE
| Code: |
| http://rapidshare.com/files/209413025/GTACWptched.rar |
MEGASHARES
| Code: |
http://d01.megashares.com/?d01=df31b81
|
Only for CYCLO DS EVO& EDGE users
Patched Rom version 2
MEGAUPLOAD
| Code: |
| http://www.megaupload.com/?d=GJ6RQEWP |
RAPIDSHARE
| Code: |
| http://rapidshare.com/files/209514304/GTACW_cyclo_.rar |
MEGASHARES
| Code: |
| http://d01.megashares.com/?d01=0e174fa |
I personally tested version 1 rom on M3 ds real and it's been working fine. No saving problems at all. Should be working with most flashcarts as well.
All patching are done. Just put the .nds file to your memory card and you're good to go. No further patching required.
Update: Some particular flashcarts require individual fix. Ensure that you have updated to the latest firmware of your cards. So please report whether it is working with yours or not, then we can establish this works with what flashcarts.
So far version 1 rom works with:-xxx(confirmed by..)
-M3 DS Real(Me)
-M3 Simply(Me, UseSoap)
-R4(most posters)
-R4 III SDHC(cribber)
-NDSTT(craigy, Vyrl, hasmed, javid, b_suave32, )
-Acekard Akaio(tigger69, Lakerchick1979)
version 2 works with:
-EDGE(thfcmad)
-CycloDS(fonzi)
-R4(fonzi)
..and the list continues as more feedbacks are received
Update#2: About multiplayer aspect, unfortunately this patched rom still cannot function well in that regard. Neither local nor online multiplayer mode worked for me. Perhaps we will have to wait a bit longer for a fully functional version of this game or new firmware from flashcarts manufacturer. Until then, just enjoy the singleplayer mode first. Of course if someone succeeded, you're most welcomed to report your findings.
Link checked on Sun Mar 22, 2009 2:49 pm [WBB_Linkchecker_Bot]