under what conditions will disconnecting the ALDA boost line produce better performance?

i do not have a boost gauge... i wanted to find out if I had boost or the lack of it so i disconnected the boost line to the ALDA to get a baseline. Lo and behold, the car "seems" to be more responsive below 2.5k rpm... and slightly better above 2.5k rpm with the boost line connected. whuttda?

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project