Help with downgrade BB on iphone 3g (yes i have bl 5.8)

[gdaniels13]

what my end goal is to jailbreak my iphone to ios 3.1.3 without using spirit, it currently has the 5.13.04 baseband and with every method other than spirit it fails, the reason i dont want to go to 4.2.1(that installs just fine) is that it is way slow an laggy. i was thinking (correct me if i'm wrong) that if i had the downgraded to firmware 5.11.07 or the 4.26.08 then i could restore to stock using itunes with the 3.1.3 (right now itunes errors out 1015 i can use tiny umbrella to kick it out of recovery but then the only jailbreak that will work is spirit and from what ive read and tried its not as good as the others)

when i got th iphone it was on 4.2.1 with bb 6.15 and ive used fuzzy band to downgrade the bb i was thinking that there would be some way of getting an older release of that to downgrade.

also i am a noob at this so let me know if i'm on the wrong track
thanks

[goofball2k]

Use tinyUmbrella to see what SHSH may be saved on saurik's server for your phone. Unless you have SHSH blobs, you don't have a choice on what IOS version to install, you're stuck with what Apple is signing for your 3G (which is 4.2.1)