4KQ new battery

[DQVT74A@prodigy.com ( CHANGLONG HUNG)]

Hi all, 

Lately, my 4KQ has been running poorly and very sluggish from 1-3K 
rpm.  Today, I could not start my 87 4KQ and figured the battery is 
dying.  So, I took out the old Interstate battery and went to Pep 
Boys for a new one.  Only one they have is Pro Start(house brand). It 
is cheap at $43.  Does anyone have any experience with Pro Start?  I 
was actually looking for Optima battery but could not find one.  I 
bought the Pro Start and put in the car and it starts fine.  Funny 
thing is with the new battery, the sluggish in low RPM is gone.  The 
car runs great again.  Why?  My guess is the low voltage probably has 
caused the injector to run lean.  Ca someone please tell me the real 
reason?  I can handle the truth.  :)))  TIA.

Sammy
'87 4KQ