relevant to the items you mentioned
>> So I am looking to get new injectors, seals, lines, and connectors.
The seals I get from DiFatta, but they're strangely pricey. You might consider getting Bosch injector seals from a BMW or M-B shop. The rubber lines for the high pressure fuel areas is a special high-pressure fuel line for injected cars, not the low pressure line from carbureted cars (although this might work for the return line, I'd use the other stuff for uniformity's sake). The 7.5mm hose is recommended (for 164 and Spiders, probably for Milano too) but I use the 7 mm hose available from VW shops and have had great results without leaks. You might have to get the 3x7 mm hose on-line, as the shop I'd found near me that carried it has gone out of business.
The connectors are a pain. There are expensive versions available for splicing in for $7-$12 per socket. Six to ten (depending on how many things you're replacing -- six for injectors plus IAC plus CTS plus....?) makes quite a price hit. The sockets are absurdly cheap on the bulk market, but it's hard to find everything at one place.
On the injector topic, I'm sorry to sound like an echo of Del, but why replace the injectors? They have a great lifetime and I've not heard of any going bad. If you're going up in displacement or supercharging, then you might need more fuel than they can supply within the available duration. But otherwise? Seems like money you'd better spend on injector connectors. Sorry I don't have part numbers.
You can get many of the small (but standard for many cars) parts from RockAuto. There's a 5% disount code posted in this forum or the 164 forum fairly often. I thing there's one up currently. They should have the injector seals listed for a suitable BMW or Merc. Sorry I don't know which model. Seals are reasonable to replace.
Michael