Spool up
I have driven back to back my '01 with PDR HX40, then an "02 with PDR HX40/HT3B twins. I really can't feel any difference in initial spool up. Both have the same air filter [AFE] and are running the same fuel box [drag comp] and similar injectors.
Leaving a stop light, or stop sign, I can't measure or percieve any difference in spool, but once under way, and making some boost, the twins will create much more boost under similar amounts of throttle compared to the single.
And most importantly, cruising down the road, the twins will create almost instant boost while the single has some lag.
The single charger truck can see over 1400* at will on the freeway during a 80-100mph blast, while the twins are hard to get over 1200*.
Twins are in my future!
Greg L