[kitcarbp]

Pics would help here along with a few more details, since I dont know the shroud set-up you are now using and the rad type difference before and after. Did you change anything else, water pump or pulleys ?
Is the 16 " a puller set-up or pusher ? Were the prior twin fans puller or pusher ?
The SPAL fan if shrouded correctly should be OK. Do you know your peak HP on the engine, mild or wild ?
Based on 22 amps ,sounds about right, the rule of thumb is 10 amps per 1,000cfm with most motor/blades, and will depend on static air pressure drop, SPAL does a nice job telling you what cfms to expect from theor fans based on rad core air resisitance (pressure drop). Ensure you have 13V minimum voltage across fan connector with the fan running, if so the fan and wiring are OK. (double check and make sure fan is running the direction intended (pulll or push) . Yes air inlet flaps would help but before I see pics of the shroud cant confirm. To easily diagnose, run the set-up without the shroud but with fan mounted and if temps drop back to where they were while cruising without fan running , then shroud needs to be improved. If no change in temps is seen, the rad is not correct for your application. Speak to folks at Griffin Radiator or Ron Davis or your favorite rad supplier for advice.

The fact that your temps are higher while cruisng immediately after the rad/shroud change, points directly to the rad or shroud combo. What are the old and new rad core dimensions? Are you now using a different core style or size? More rows of tubes, different tube sizes ?

What % of core does the fan cover ?

The target temp needs to be about 190F engine out (upper hose), steady-state (fully warmed and driving highway speeds). A properly sized cooling system will have engine inlet temp of about 180F (lower hose), thats the target you should aim for. In other words the delta T should be 10F but 15F is OK also across the rad. 180F thermostat is fine as long as its functioning correctly, don't change it to a 160F.