I thought it would be helpful to post some data on fuel injector mods, since my last two purchases did not go well. I'll get started with an outline and edit in more details/updates when time allows.
1) OEM # 25313185
Blazer, Envoy, Bravada / 28 lb/hr
2) Stock 1999 Alero V6 / 19 lb/hr
3) RC Engineering SL2-370 / 35 lb/hr
4) Lucas 42.5 / lb/hr
Notes (results may not be typical / running at high altitude / stock fuel pump) :
1) Envoy Injectors (4-hole nozzle)
I have had great results with these -- excellent drivability. When I first got them they worked well enough without reprogramming the computer -- initially threw a "rich" code, but adjusted itself out. I am the 3rd owner of them. Even though often run up to 108% duty cycle, seem to perform better than their flow rating.
2) Stock 1999 (6-hole nozzle)
3) RC Engineering SL2-370
These came with a flow rating for each injector, as if they had been individually tested before shipment. According to the data sent with them, they were matched within + or minus 1 cc (!) Three flowed at 370, two at 369, and one at 371 cc, said the chart. They didn't indicate which was which, but if they were that close, it wouldn't matter. The first time I ran them in the car, I thought "Wow, they're great ! " Midrange up to WOT was smooth, powerful, had a precision feel. But soon, as the car warmed up and the computer settled in, an off-idle stumble developed. Not just from a standing start, but also a hesitation when stabbing the throttle from a low rpm cruise. This was accompanied by a little black smoke out of the tailpipe each time, and random misfires but no codes thrown. Eventually the computer's compensating made matters even worse. I tried every possible tuning combination to get a usable result, but none worked.
I'm guessing the single-hole spray nozzle was just not atomizing well enough at the low Injector Pulse Width required.
4) Lucas 42.5's
I got these from ZZP over a year ago, not flow matched. I ran them through the Winter and into the Spring. In colder weather during startups, I got misfire codes thrown, but no SES light. After warmup, no codes appeared. In spite of that, the car idled OK and did not hesitate or stumble. Performance seemed to be generally good. But then, one day at the track, the # 5 Injector stuck open. Performance at the track that day had been subpar, but until it failed completely it was not obvious exactly why. The car had to be towed home.
When I called ZZP and asked to get one replacement, the guy said they can only be purchased in a full set.
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