first off, you might wanna replace some rubber if you haven't already done so. I recommend (if you haven't already done so) checking your coolant hoses, vacuum lines (you can buy the whole "harness" from the dealer), plug wires, flexible brake lines and of course tires.
As for a reliable mods list:
3" downpipe (the zzp catted one is a good choice and a quality piece)
PLOG (don't buy a mild steel one if you find one, they crack)
FWI (make one or buy one)
3.5 pulley (do yourself a favor and get an MPS just in case)
Tune (a good one, not some mail order garbage)
shift kit (transgo is popular, stock is junk)
In my experience these mods will keep the car 100% reliable.
Honestly if you did headers and rockers and a smaller pulley you would notice quite a bit more gain in power. However, with headers there is a potential to F your trans and oil dipsticks, also the speed daddy 02 is in a retarded location (you get what you pay for). Using stock gaskets, copper RTV and band clamps I've had zero leaks in 2.5 years, I even snapped off one of the studs. I also have the zzp modded 1.9 rockers, I've had zero problems with them and I highly recommend them. However, there is always a risk of valve train failure when you start messing with that stuff hence why I did not recommend them for your maintenance free mod list.
Also, as mentioned above you can greatly increase your handling/ braking with some suspension/ brake mods on the cheap. (honestly it's more of a safety thing than performance....try a panic stop at 80 on the freeway and let me know how much confidence you have in the stock 11" junk).
I would recommend the GMPP suspension kit, it comes with front and rear sway bars, endlinks, rear trailing arms and a strut tower brace (garbage, threw it away). I bought the kit back in 07 for 100 bucks, huge bang for the buck, way less body roll. This is also beneficial since it will replace some of your rubber underneath which is sure to be dry rotted. I would also recommend doing a 12" brake upgrade. All you need is a set of front rotors and caliper brackets from an 2000 impala (other years will work but it's easy to remember since it's the same year as your car), everything else works. Just make sure you don't have the cross laced wheels, the larger brakes have interferance issues. I waited till I needed brakes and did the upgrade for like 50 bucks since you'll need rotors anyway. Huge diffence in brake feel, fade, it's a no brainer and I wish I had done it soon. Sure there are better kits but at what cost?
I hope you take this serious as this advice comes from experience aaaaaand I didn't write it for my health.
