no power low rpm

I have A 78 kz650d1 Kerker 4-1, Pods, Main Jet 115, Pilot 15, Needles one up, Clean & rebuilt. Fuel screws 1.5 turn. New carb boots too.
Runs great except...
If I try to accelerate hard in 1st gear, it bogs down. If I roll the throttle slowly and let it get up to 2500-3k I can gun it. The only way I can accelerate fast off the line is to rev it and let the clutch out slowly untill it hits about 3k and then it roars. Also I have a bit of backfiring thru the carbs. If roling at idle and I open the throttle it bogs down and almost dies. I'm going nuts! I had some smartass on a new 150cc scooter pretty proud of himself for beating me off the line. HELP!
Blake

One more note- It sounds like a friggin popcorn popper when I try to accelerate in a high gear from 1500-3000rpm ! I lowered the needle clip today to the 4th clip - one up and got more mid & top power but now I got popcorn!

first...these things dont like to lug...keep your rpm's up higher or downshift. maybe your timing advancer is stuck? i think id check that first. for me normal cruising rpms are around 4 to 6 grand..any lower downshift...try this first...steve

how new are the carb boots? I ask because I had the exact same symptoms right after I put my carbs back on. I didn't have a good airtight seal around my carb boots and it was sucking in air. It was a real pain in the neck to wrestle with until it no longer took in air.

Brand new boots. I think I just need to take it apart and put it back together again. I'm also having the Pilot's drilled up to 20's from 15's. I'm also going to do a compression test as well. Just waiting for the weather to clear so I can pull of the cover and get started.

Blake