e44i5...sounds like your SPF is FINE, but you have an ENGINE/ALT problem, no ? just wondering as SPF does not do engine installs and you had me worried there for a minute that there was a car problem.
I can't help ya with your alt issue, added a radio to mine with power amp and since 1996 car has same alternator and one new battery and no problems. Heat has been known to take its toll on the alternators and underdrive pulleys seem to perplex some too.
However, I am sure someone else will chime in and help ya out as many have been converting to the 100 amp single wire alts with built in volt regulators as can be found for sale on the Performance Unlimited site :
www.performanceunlimited.com . they are chrome too , look kinda spiffy under the bonnet of any Cobra experiencing similar problems. bill.