1. Get a fuel pressure gauge. Or borrow one from a local MN member.
Check the fuel pressure and make sure it meets minimum factory specs.
2. Inspect your exhaust manfolds for cracks (very likely that you have them). They
are very hard to see. Get them repaired if you do.
3. Make sure you have a scantool available when it warms up in the spring.
IF your fuel pressure is good, and you found no EM cracks or had them repaired, 2.3" is probably the safest bet with no exhaust mods.
If you have to remove the EM'* to repair cracks, have the outside of each runner stitch-welded by a shop that knows exhaust. Then grind out the OEM weld on the inside. Perhaps a 2.2" pulley at that point.
The Series 1 L67'* are getting picky in their old age. You can destroy your motor if you don't follow this advice closely. Scanning for KR this time of year will usually tell you nothing, as you'll have KR in the summer, but not in cooler temps.
We had a member quite recently that blew his motor by not heeding the above advice. Pulleys are not plug/play. Each step in pulley size requires more and more work to support it.
ALWAYS run 91 octane minimum, even with a stock pulley.
You need a scantool and a fuel pressure gauge, but honestly, if you intend to mod the car, and your list of mods includes a pulley, you should OWN the scantool and fpg. You'll need to scan in the spring and a couple more times each summer.
Is there any other way to find cracks and leaks in the manifold without a microscope.. ....some kind of solution to put on them. See I build exhaust for Cummins and we use this stuff called snoop but the exhaust isn't being used it'* just put under air pressure..