Some help please
 

So today on my way home from work i when to do a 3 gear pull was going rich than after like 3.5 grand it when full lean let off and did another pull same thing let off what can it be. i have a blow downpipe gasket where the header and downpipe meet that i am replace soon but it leaken pretty good could that cause it? or what can it be??

water could have gotten on the maf sensor and is messing your fuel trims up happened to me when i had the supercharger.